Midterm #2 Flashcards
Basic division of human nervous system
- Central nervous system
–> Brain
–> Spinal cord - Peripheral nervous system
–> Somatic nervous system (skin, muscles and joints send signals to the spinal cord and brain), (Brain and spinal cord send signals to the muscles, joints, and skin)
–> Autonomic nervous syste, (Glands and internal organs send signals to the spinal cord and brain), (Brain and spinal cord send signals to the glands and internal organs –> further divided into sympathetic nervous system, and para-sympathetic nervous system).
Somatic Nervous System (SNS)
Transmits signals to CNS from muscles, joints, skin via nerves. CNS sends signals through SNS to muscles, joints and skin, to initiate, modulate, or inhibit movement.
Autonomous Nervous System (ANS)
Regulates internal environment of the body. Stimulates glands, and organs. Nerves of ANS project signals from these targets to CNS. Divided into sympathetic and parasympathetic system. They are opposing systems in terms of outcomes.
Sympathetic system
Signalling “fight or flight”; prepares body for action. Chronic stress leads to increased activity of this system.
Parasympathetic signalling
Signalling “rest and digest”; returns body to resting state.
Endocrine system
A communication network that influences thoughts, behaviours, actions. It works together with the nervous system. Signals slower than nervous system. Uses hormones to influence brain and body. Primarily controlled by hypothalamus, via signals to the pituitary gland.
Hypothalamus-pituitary-adrenal gland axis (stress response) in endocrine system
Hypothalamus secretes hormones corticotropin-releasing hormone (CRH) that stimulates pituitary to release adrenocorticotropic (ACHT), which increases cortisol production of the adrenal gland. Cortisol, on the other hand, inhibits production of CRH and ACHT, in a negative feedback loop.
Building blocks of Central Nervous System (CNS)
Neurons and Glial cells
Basic function of Neurons in CNS
Communication in form of propagating electrical signals
Basic function of Glial Cells in the CNS
Support and contribute to functions of neurons. There are microglia and there are macroglia.
Microglia glial cells
Protect CNS neurons. They are smaller than the other glial cells, and are mobile within the brian. They can metabolize dead tissue and are involved in keeping the CNS healthy.
Macroglia Glial cells
Astrocytes and oligodendrocytes are macroglia. Astrocytes link neurons to blood vessels, forming part of the blood-brain barrier, and they engulf synapses which regulate neurotransmitter release during synaptic transmission. Oligodendrocytes surround axons in the CNS, forming the myelin sheath that insulates axons, which allows the electrical signal that travels in the axons to travel faster.
Three basic types of neurons
- Multipolar interneurons (connect neurons with other neurons)
- Motor neuron (send information from CNS to the body’s effectors)
- Sensory neuron (act as receptors of stimuli, or are connected to receptors).
Anatomy of neurons
From cell body (soma), two kinds of cytoplasmic processes extend: a) one or more dendrites, and b) a single axon. Neurons can have different shapes, depending on their function and location.
Steps for information flow in the neuron
- A signal is received at the dendritic spines, at the post-synaptic terminals, where the neuron synapses with the axon of another neuron.
- This signal can produce an electric current that travels from the dendrite to the soma of the neuron.
- If the signal accumulating at the axon hillock in the soma is strong enough, the receiving neuron will “fire”.
- This electrical impulse travels down the axon toward the terminal buttons.
- When the electrical impulse reaches the pre-synaptic trminal, it can produce a chemical signal: the release of neurotransmitters.
- When neurotransmitters reach the post-synaptic terminal of the receving neuron: go back to point 1.
Electrical potential
Refers to how much energy is stored up in a system. When battery poles are connected in an electrical circuit, the potential can be released and converted for example in light energy.
The resting potential
At rest, when a neuron is not active, the electrical charge inside and outside the neuron is different. This difference in charge is called a potential. A neuron at rest has the resting potential of around -70 millivolts.
A brief change in the resting potential
If the electrical stimulation is strong enough, it exceeds the threshold of excitation and the axon of the stimulated neuron will fire an action potential. During the action potential, the neuron is briefly depolarized, so the membrane reaches about +40 mV.
Diffusion
Diffusion: refers to the phenomenon that particles tend to move from a region of high concentration to low concentration, eventually reaching an equilibrium of equal dispersion. Diffusion results from Brownian movement, which correlates with temperature. It is a force that pushes particles down their concentration gradient.
Electrostatic pressure
Refers to the fact that equally electrically charged particles repel each other, and differently charged particles attract each other. Applied to neurins: negatively charged molecules (anions), tend to move away from each other, and so do positively charged molecules (cations). Anions and cations are moving towards each other.
Ion channels in the neuron membrane
There are proteins in the neuronal membrane that form little channels, connecting the inside of the neurons with the outside. Some of these proteins allow certain types of ions to pass. These channels are called ion channels (example: sodium channels, potassium channels.) Some ion channels only open under certain conditions. These channels are called dependent ion channels.
Concentration of ions inside the neuron at rest
At rest, the concentration of negative ions inside the neuron is larger than outside, which has more positively charged particles than the inside. Unequal distribution of K+ and Na+ causes resting potential.
The resting potential: diffusion and electrostatic pressure
In the extracellular space (space outside neuron), we find a lot of NaCl in the solution, we also find K+. In the intracellular space (inside neuron), we find many negatively charged large proteins, K+, and about equal low amounts of Na+ and Cl-. As a consequence, during rest, the inside of the neuron has more negatively charged particles than the outside. This is why resting potential of neuron is negative.
Dynamics of diffusion and electrostatic pressure that determine resting potential.
Cl- is in greatest concentration outside, diffusion forces it inside. However, because there are many negatively charged organic anions inside, electrostatic pressure pushes Cl- out. K+ is higher concentrated inside, diffusion therefore pushes it out. However, the outside is positively charged, therefore at the same time electrostatic pressure pushes K+ in. Na+ is in greater concentration outside, so diffusion forces it inside. At the same time, electrostatic pressure pushes Na+ also inside. This is why there is the sodium potassium pump. Organic anions (negatively charged) cannot leave the neuron.
Ion flow during action potential
Resting potential at -70mV. Then an electrical stimulation exceeds threshold of excitation:
1. Sodium channels are voltage dependent channels: they open, and Na+ rushes into neuron (driven by force of diffusion and elecrostatic pressure.) this depolarizes the neuron membrane potential.
2. When depolarization reaches a point close to 0 mV, potassium channels open. K+ leaves neuron due to force of diffusion, and driven by electrostatic pressure from inside due to increase in positive charge from Na+ influx.
3. When depolarization reaches about +40mV, the sodium channels enter a refractory state and close: no more Na+ can enter the neuron.
4. The forces of diffusion and electrostatic pressure continue to force K+ out of the neuron. This reduces the positive charge inside the neuron, repolarising it.
5. When potential reaches resting potential, K+ channels close.
6. There is a slight hyperpolarisation, neuron reaches -70mV. Sodium-potassium pumps restore resting potential.
Release and Binding of Neurotransmitters
Neurotransmitter binding, depending on the transmitter and the receptor, can have a variety of outcomes. Some can hve an inhibitory effect (make it less likely that the post-synaptic neuron will fire). Some will have an excitatory effect (they make it more likely that the post-synaptic neuron will fire.
Control of Neurotransmitter Release
Synapse consists of: presynaptic terminal, synaptic cleft, post-synaptic terminal. It also includes glial cells that enclose three parts.
Three parts of synapse that glial cells enclose
Autoreceptor: senses the amount of released neurotransmitter to regulate exocytosis (release of neurotransmitters).
Reuptake: a reuptake mechanism “recycles” neurotransmitter from the synaptic cleft, moving it back into the presynaptic terminal. Some antidepressants interfere with this process for the neurotransmitter serotonin.
Enzymatic degradation: enzymes in the synaptic cleft degrade released neurotransmitters.
Summary of core events and concepts of signal transmission pt.1
When action-potential reaches the pre-synaptic terminal, it is converted from an electrical signal into a chemical signal. First, the action potential causes Ca2+ entry into the presynaptic terminal. This promotes that vesicles loaded with neurotransmitters (proteins) fuse with the presynaptic membrane. This causes neurotransmitter to be released into the synaptic cleft. There, they diffuse and eventually bind to receptors (proteins), that swim in the membrane of the post-synaptic cell.
Summary of core events and concepts of signal transmission pt.2
There are several different different types of receptors in the post-synaptic membrane of neurons in the CNS. Each receptor can bind a particular neurotransmitter. Binding the neurotransmitter can cause a specific action of the receptor. Now the chemical signal has been converted back into an electrical signal. This influx of electrically charged molecules can cause a depolarisation of the post-synaptic neuron, which can then lead to the neuron firing an action potential. Some neurotransmitters can have have the opposite outcome, they are inhibitory, not excitatory.
Summary of core events and concepts of signal transmission pt.3
Some receptors do not lead changes in charge when neurotransmitters bind to them, but they influence biochemical processes in the neuron, which can change the structure or functioning of the neuron. Released neurotransmitters are removed from the synapse by enzymatic degradation or reuptake into the presynaptic terminal. Some psychopharmacological drugs influence these processes.
Corpus Callosum
consists of millions of myelinated axons that connect the two hemispheres. Importance of this connection apparent in split brain patients.
Hemispheric organisation
Because the hemispheres are somewhat specialized, in split brain patients two independent forms of knowledge exist. Left hemisphere is critical for language: if split patient sees object with right eye, this is projected into the left hemisphere, and therefore the object can be named. What patient sees with left eye (projected to right hemisphere), cannot be named because right side does not have access to language system. However, patient can choose this item with the left hand (controlled by right side).
Frontal lobe principal functions
Cognition and memory. Ability to concentrate, judgement, consequence analysis, problem solve, plan, personality (including emotional traits)
Parietal Lobe principal functions
Plays an important role in integrating information from several senses. Also processes spatial orientation, some parts of speech, visual perception, and pain and touch sensations.
Occipital Lobe principal functions
Visual processing center of the brain. It contains most of what is referred to as the “visual cortex”. It is also the part of the brain where dreams originate.
Temporal Lobe principal functions
Chief auditory receptive area and contains the Hippocampus, which is the chief region where long-term memory is formed. Also deals with high-level visual processing (faces & scenes).
Brain Stem: Basic Survival Functions
Brain stem is the superior end of spinal cord. A main communication pathway between brain and body. Houses nerves that control basic functions. Reticular formation: projects into cerebral cortex, affects general alertness. Involved in sleep regulation.
Cerebellum
Essential for movement and proper motor function. For example, damage causes head tilt, balance problems. Essential for motor learning and motor memory. It operates independently. Cerebellum also involved in planning, event memory, language, emotions.
Thalamus: sensory relay
Is a gateway to cortex. With the exception of odour information, it receives all other sensory modalities. Smell, the oldest and most fundamental sense, has a direct route to cortex. During sleep, thalamus partially shuts down incoming sensory stimulation.
Hypothalamus
Hypothalamus is indispensable for survival. receives afferents from almost every body and brain region. Affects functions of many internal organs, regulates body temperature, blood pressure, blood glucose levels. Involved in motivated behaviours (thirst, hunger, aggression, lust.)
Basal ganglia
Critical for planning and producing movement. Afferents from entire cerebral cortex. Efferents to motor centres of brain stem. Damage can cause tremors and rigidity in Parkinsons’s disease, or loss of movement control in Huntington’s disease. Nucleus accumbens is part of basal ganglia, and is important for reward processing and motivating behaviour. This involves dopamine activity in the nucleus accumbens.
The Limbic System
Hippocampus essential for episodic and certain spatial memories. Hippocampus and amygdala densely connected. Amygdala processes emotions. Amygdala modulates processes in the hippocampus (and other brain regions), might signal importance of events, thus increasing their likelihood of being retained.
Psychophysics
Quantitative methods for measuring the relationship between physical and psychological events. Research aimed at relating physical stimuli to the contents of consciousness and behaviour.
Absolute threshold
The smallest stimulus level that can just be detected (and create a conscious experience)
Single detection theory
Accounts for individual biases
Just noticeable difference (JND)
The minimum difference that must exist between two stimuli before we can tell the difference them half of the time.
Sensation
The process by which our sensory organs detect a stimulus. We receive stimulus energies from different features of the environment.
Perception
Interpretation of sensory information to form a conscious representation of the stimulus.
Transduction
Transformation of one type of energy into another. It’s the conversion of stimulus energies from our environment into neural electrochemical energy (action potentials, neural signals).
Bottom-Up Processing
Also called data-based processing. Processing based on stimuli (elementary messages) in our environment.
Top-down Processing
Also called knowledge-based processing. Processing based on knowledge and memory to form a representation (perception).
Cornea
Transparent element of the eye through which light passes as it enters the eye.
Iris/Pupil
Coloured part of the eye. Muscular diaphragm that regulates entrance of light through contraction of the pupil (centre of iris).
Lens
Transparent element of the eye through which light passes after going through the cornea and aqueous humour (accommodation).
Retina
Surface on the back of the eye that contains a complex network of cells, including photoreceptor cells.
Fovea
Small area on the retina containing only colour-sensitive photoreceptors.
Optic nerve
Area of the retina where cells leave the eye and transmit action potentials to the brain. Creates a blind spot.
Photoreceptors
Responsible for the transduction of light into neural activity.
Cones
Respond better to bright light (daylight vision). Sensitive to specific wavelengths of visible light. Responsible for high-resolution (colour) vision. Around 5 million on the retina of each human eye.
3 types of cones
- S-Cones: Short-wave length cones (blues)
- M-Cones: Medium-wave length cones (yellow, greens)
- L-Cones: Long-wave length cones (orange, reds)
Rods
Respond better to dim light (nighttime vision). Sensitive to all wavelengths of visible light. Black and white vision. Very low resolution. Around 100 million rods in each human eye.
Location of photoreceptors on the retina
Rods are mostly found on the periphery. Cones are mostly found in the fovea.
Blind Spot
Where the optic nerve leaves the eye. There are no photoreceptors. The visual system usually fills in the blindspot with information from surrounding area.
Bipolar cells
Intermediate retinal neurons that receive input from the photoreceptors and send signals to retinal ganglion cells.
Diffuse bipolar cells
In the periphery. 1 diffuse bipolar cell responds to around 50 rods. Increased sensitivity but reduced acuity (50 rods; 1 diffuse bipolar)
Midget bipolar cells
In the fovea (centre). Receive input from a single cone and pass neural signal to a single ganglion cell (1cone: 1 midget bipolar).
Neural Convergence
Occurs when a number of neurons synapse onto a single neuron. Perception is shaped by neural convergence. Signals from rods converge more than signals from cones. Rods have better sensitivity than the cones, and cones have better acuity.
Ganglion cells
Retinal neurons that receive input from the retinal bipolar cells. Axons of ganglion cells leave the eye through the optic nerve.
M-Cell
Large ganglion cell. Mostly respond to rods via diffuse bipolar cells.
P-Cell
Small ganglion cell. Mostly respond to cones via midget bipolar cells.
A neuron’s receptive field
is the area on the receptor surface (retina) that, when stimulated, affects the firing of that neuron.
Center-Surround antagonism
Center-surround fields contribute to edge enhancement, causing an increase in perceived contrast and making edges look more distinct. This is true whether it’s day or night, whether indoors or outdoors, etc.
Trichromatic theory
Theory of colour perception stating that our three types of cone cells are each more sensitive to a specific wavelength of light and work together to produce colour perception. Our perception of colour is specifically determined by the ration of activity in three receptor mechanisms.
Opponent process theory
Theory of colour perception stating that information from the cones is separated into three sets of opposing/opponent channels in ganglion cell layer: Red-Green, Blue-Yellow, Black-White
Feature Detector cells
Receptive fields of individual neurons in V1
How does the visual signal get from the retina to the visual area of the cortex?
Information from the retina leaves the eye from the optic nerve. Information from the optic nerve travels to the optic chiasm (crosses over). Information reaches the lateral geniculate nucleus (LGN) of the thalamus.
Information reaches the Visual cortex/Striate cortex/V1.
Orientation selectivity
Receptive fields of striate cortex cells are not circular like the RGCs fields, but more elongated.
Simple cortical cells
Neurons fire more when the bar has a specific orientation.
Complex cortical cells
Neurons fire more when the bar of light has a specific orientation and specific movement.
Once visual information has reached the cortex, how is it processed?
Ventral stream: “What” stream. Visual information is processed in the temporal lobe (responsible for object recognition). Dorsal stream: “Where” stream. Visual information is processed in the parietal lobe (responsible for location of objects in space).
Perceptual Organization
The process by which elements in a person’s visual field become perceptually grouped and segregated to create a perception.
Gestalt Principles
Describes how people tend to organize visual elements into whole entities. Gestalt psychologists believe we are born with specific predisposed ways of organizing information so that it has utility.
Principle of Proximity
Elements that are close together appear to be grouped together.
Principle of Similarity
Similar things appear to be grouped together
Principle of Closure
Objects that appear incomplete are perceived as being full/complete. People perceive the whole by filling in missing information.
Principle of Good Continuation
Points that, when connected, result in straight or smoothly curving lines are seen as belonging together, and the lines tend to be seen in such a way as to follow the smoothest path. We also assume that objects continue even if we cannot see it.
Principle of Common Fate
Objects that appear to move together are perceived as grouped together.
Principle of Figure-Ground
The eyes differentiate an object from its surrounding area. A form, silhouette, or shape is naturally perceived as figure (object), while the surrounding area is perceived as ground (background).
Principle of figure-ground
The eyes differentiate an object from its surrounding area. A form, silhouette, or shape is naturally perceived as figure (object), while the surrounding area is perceived as ground (background).
Cortical blindness
Damage/lesions in the visual cortex leads to cortical blindness. Typically occurs only on one side - blindness in the opposite visual field (“half-blind”). LGN and lower pathways still intact.
Blindsight
Patients with cortical blindness can still react to and identity stimuli presented in their blind visual field, above chance level. (Identify object shape localize objects, detect emotions in face).
Visual agnosia
Inability to recognize visual objects, but can still see colours, shapes, faces.
Prosopagnosia
Inability to recognize faces. Patients show emotional responses to very close relatives.
Akinetopsia
Inability to detect motion. Patients see life in a series of snapshots.
Sound
Vibrations in a medium (air/water) that cause pressure changes or waves.
Frequency
For sound, the number of times per second that a pattern of pressure change repeats. Perceived as pitch
Amplitude/Intensity
The magnitude of displacement (increase or decrease) of a sound pressure wave. Perceived as loudness.
Outer ear
Pinna: outer segment of the ear –> shaped to collect and funnel sound toward tympanic membrane.
Tympanic membrane: also known as the ear drum. Transfers sound energy from air to the ossicles.
Middle ear
Ossicles: amplify sound arriving at the eardrum to the oval window (small membrane) of the cochlea. (Malleus, Incus, Stapes).
Inner ear
Cochlea: fluid-filled, coiled, structure. Within the cochlea are two membranes which create three canals. Basiliar membrane: where the hair cells (sound transduction) are located. Tectorial membrane: floats above and connects to hair cells.
Hair cells
Transduce mechanical movement from sound waves into neural activity. Fluid vibrations from sound cause the basiliar membrane to move (ripple). This movement causes the cilia of hair cells which are attached to the tectorial membrane to bend. The bending of hair cells causes a neural signal to be sent down the auditory nerve.
Place theory in interpreting sound
The brain uses the location of neural firing to understand sound.
Frequency theory in interpreting sound
The brain also uses information related to the rate of cells firing. The more rapidly the cells fire, the higher the perception of pitch.
Auditory pathway
Auditory information travels to medical geniculate nucleus of thalamus. Auditory cortex in temporal lobes.
Tonotopic organisation
The spatial organization of the basilar membrane is maintained through the auditory pathway.
Sound localization
Detection objects location in space relies on Binaural cues (auditory cues that require comparisons from both ears). Interaural time differences: differences in arrival times at each ear. Interaural level differences: differences in the intensity of sounds that reach each ear.
Mechanoreceptors
Transduce mechanical stimulation (pressure) into touch sensation.
Merkel recpetor
Application and removal of pressure (constant firing while pressure applied)
Meissner Corpuscle
Application and removal of pressure (fire only during the application and removal - changes in pressure).
Ruffini cylinder
Interpret stretch of skin
Pacinian corpuscle
Vibration and texture
Thermoreceptors
Sensory receptor that signals information about changes in skin temperature. Two distinct populations; warmth & cold fibres. Also respond to chemical stimuli.
Nociceptors
Sensory receptor that transmits information about noxious (painful) stimulation that causes damage or potential damage to skin. Mix of signals transduced: mechanical, thermal, chemical.
Somatosensory cortex
Relayed via thalamus to contralateral parietal lobe. Somatotopic organisation: Spatially mapped in the somatosensory cortex in correspondence to spatial events on the skin. Adjacent points on your skin are represented by adjacent points on somatosensory cortex.
Body schema modifications
Visual input integrates with and even overrides our conscious body image. Tools can become integrated into body schema.
Narrative
Our brains have a natural tendency to find meaningful patterns and causality in our surrounding world. We can not only combine prior knowledge to perceive what something is but we can also assign a deterministic cause for what we perceive.
All-encompassing narrative
We tend to find patterns/narrative that explain all variables and this seems to be a form of adult human perception.
Split-brain patients
Corpus callosum is severed - communication between the left and right hemisphere is impaired.
Hemisphere organisation
Because the hemisphere are fairy specialized - in split brain patients, two independent forms of knowledge exist.
The interpreter
Left-brain process which generates narrative. Causal explanations (narrative) are generated by the left-hemisphere. Combines already known knowledge with ongoing events to infer causation.
Participants watch a movie in a fMRI scanner and then recall the story immediately afterward
Synchrony in spatial brain activity across participants whilst watching the same movie. Synchrony in spatial brain activity within participants between watching the movie and verbal recalling the movie. The greatest synchrony of brain activity patterns occurred between participants during the recall session.
How do kids acquire language?
Learned. Humans only.
Is there evidence for prenatal learning?
Yes (cat in the hat study, native vs. other languages study). But, everything might not be learned (speech preference study, language discrimination)
Cat in hat study
Mothers read cat in hat book to children before they are born. When they are born they do an experiment with them sucking on a pacifier. Every time they do a short suck they play a short snippet of cat in the hat. Some kids get played cat in hat, some get played dog on log. Kids that hear cat in hat end up shortening their sucks, but kids that got played dog on log have no effect. This is because cat in the hat is more rewarding because it was read to them before.
Point of origin of modern memory research
Bilateral hippocampectomy to treat epilepsy led to temporally graded retrograde and dense anterograde amnesia (you cannot encode new things) for episodic memory. Other forms of memory, however, remained unaffected.
Paradigms of Patient HM
Explicit paradigm: (can you put this object in the bag? then go back the next day or later that day and show same object and ask if he has seen it before.) HM’s was impaired compared to normal people
Implicit Paradigm: (show him a picture of an object that goes from highly fragmented to less fragmented until they recognize what the object is) HM’s was similar to normal people’s.
Memory dissociations after hippocampectomy
Impaired: Episodic memory, recognition memory for recent objects/places, explicit memory tasks. Preserved: semantic memory, priming, procedural memories, conditioning, implicit memory tasks.
Research lines originating from HM case
Memory systems, circuitry/computation, synaptic plasticity
Declarative memory
Splits into episodic memory and semantic memory –> hippocampus - medial temporal lobe
Nondeclarative memory
Splits into procedural memory (striatum; motor cortex; cerebellum), Priming (neocortex), classical conditioning (amygdala; cerebellum), Non-associative learning (reflex pathway).
Working definition of memory
Ability to use or revive information that was previously encoded or processed. Memory is never directly observed. Its existence is inferred. No agreement as to what counts as memory. Memory does not exist physically.
Memory has a fundamentally dynamic process
Understanding memory requires a holistic perspective. The ability to form and use memories arose to solve adaptive problems. Memory therefore is fundamentally flexible and adaptive. Understanding memory is related to and may aid in answering the hard question - relation between brain and consciousness?
Different scopes of plasticity
Plasticity is a change in neuronal morphology as a response to environmental stimuli. Synaptic plasticity: refers to the phenomenon that the morphology of connections between neurons can change as a function of experience. Cortical plasticity: Refers to the phenomenon that cortical organisation can change in response to changed demands but also in response to brain injury, such as strokes, lesions, etc.
Cortical reorganisation during visual deprivation
In healthy individuals with normal vision, occipital areas receive predominantly visual input. To a lesser extent, these areas also receive tactile and auditory input. When visual input is blocked for prolonged periods, the occipital lobe receives no more visual stimulation. As a consequence, auditory and tactile stimuli recruit more processing resources from the occipital regions than before.
Example of cortical plasticity: in the blind
fMRO activation in patients reading Braille shortly and long after blindness had set in. Shortly after blindness, there is less activation in the occipital cortex during the tactile experience of Braille reading than after longer periods of blindness (and more experience with Braille reading).
The Ribot Gradient
Law of regression: The progressive destruction of memory descends progressively from the unstable to the stable. (memories are more unstable at the beginning)
Retrograde Amnesia Gradient
Amnesia more likely for recent than for remote memories. There is a process that stabilizes memories from a weak state to a stable state.
Consolidation Hypothesis
Perservation-Consolidation hypothesis: the tendency to perseverate might serve to consolidate the associations among the syllables. Current consolidation “dogma”: Memories are labile after acquisition and are fixed, i.e., permanently stored (consolidated) over time. Consolidated memories are stable and can persist long-term. Consolidation is a transient, unidirectional process that occurs only after acquisition. Disrupting consolidation impairs memory formation and therefore reduces what will be retained.
Synaptic (or cellular) Consolidation hypothesis
Learning leads to changes in the connections between neurons. These modifications are unstable at the beginning, shortly after learning. In order for long-lasting memory to for, the synaptic modifications need to stabilize. The process that stabilizes these changes is called synaptic consolidation.
Systems Consolidation
Certain types of memories initially require the hippocampus. Over time, these memories undergo a transformation in terms of which brain structures are mainly involved for their expression. This process is called systems consolidation. During this process, the expression of these memories will involve the hippocampus less and less, but more and more frontal areas.
Dendritic Spines
Small membranous compartments protruding from dendrites that house the essential postsynaptic components (post-synaptic density, cytoskeleton and supporting organelles) and receive synaptic contacts from glutamate-releasing axons.
Learning-induced morphogenesis to dendrites
Training (trace eyeblink conditioning) increases the number of spines (i.e., synapses) in the rat hippocampus.
Spine Dynamics: Sprouting & Pruning
During learning, new synaptic connections develop quickly. During the consolidation period only some of these new connections will survive: long-term memory seems more efficient than memory shortly after acquisition, in that it requires less resources to be retained than shortly after learning.
Long-term potentiation (LTP) as a cellular model of memory
Experimentally induced by high-frequency (tetanic, or HFS) stimulation of certain types of neurons in certain brain areas. Results in long-lasting strengthening of synaptic connection between neurons. As a result, firing of neurons more likely given non-tetanic stimulation.
LTP Increases size of spines and neurotransmitter sensitivity
LTP increases sensitivity of hippocampal neurons to spatially highly restricted (arrow) application of the excitatory neurotransmitter glutamate. The increase of glutamate response was measured 2h after LTP induction. Spine size increase suggests that more glutamate receptors are present at post-synaptic side. Therefore, glutamate release activates more receptors, and leading to a stranger depolarization, which increases the likelihood that the neuron will fire.
Hebb’s dual process memory model
Hebb’s First Postulate: the principle of associative learning:
An experience is represented in a pattern of activity in a set of connected neurons that can be distributed across brain regions (cell assembly). This pattern can stay active on its own for a while after the exprience. Recurrent connections among neurons of the cell assembly keep the pattern activated. This supports “short term memory”. After a while, recurrent activity leads to changes in the synapses of the cell assembly. As a consequence, the pattern can be recreated at a later time. These structural modification support “long-term memory”.
Time-limited involvement of hippocampus in memory
Bilateral hippocampectomy to treat epilepsy led to temporally graded retrograde and dense anterograde amnesia memory. Other forms of memory, however, remained unaffected.
Schemata
Schema refers to an active organization of past reactions. That is, whenever there is any order or regularity of behaviour, a particular response is possible only because it is related to other similar responses. Determination by schemata is the most fundamental of all the ways in which we can be influenced by reactions and experiences which occurred some time in the past.
Types of distortions caused by schemata
Omission: forgetting of unfamiliar material. Rationalization: attempts to increase coherence, also by considering present knowledge about the subject matter. Transformation: attempts to change the unfamiliar into the familiar.
Frame Theory
When one encounters a new situation, one selects from memory a structure called a Frame. This is a remembered framework to be adapted to fit reality by changing details as necessary. A frame is a data-structured for representing a stereotyped situation.
Definition of “script”
A memory structure for encoding general knowledge of a certain situation-action routine.
Cellular reconsolidating of auditory fear memory
Post-reactivation injections of protein-synthesis inhibitor anisomycin into the amygdala impair memory for auditory fear conditioning. Effect of anisomycin requires memory reactivation. Anisomycin only effective when administered less than 6h after reactivation.
Negative Prediction Error
Expects a shock, but no shock occurs. Propranolol reduces fear.
No prediction error
Expects a shock, and gets it. Propranolol has no effect on fear.
Positive Prediction Error
Expects no shock, but gets one. Propranolol reduces fear.
Two possible positions of retrieval or storage problem
- Nothing is ever really lost
- Real memory lost exists
Partial Report Technique
Location memory, but not identity memory decays quickly in iconic memory. Means that all letters are remembered for longer than 500ms, but the memory for which letters were in what row was lost within 500ms.
The Brown-Peterson Distractor Technique
Based on the idea that in order to measure duration of information in STM, rehearsal has to be prevented because continuous rehearsal keeps information in STM.
Procedure of the Brown-Peterson Distractor Technique
Participants are given many trials in the following form:
1. Present participant with a nonsense syllable and ask them to remember it.
2. Ask participant to count backwards in threes from a random starting number provided by the experimenter until experimenter stops this.
3. Ask participant to recall nonsense syllable.
The time interval between showing the syllable and recalling it varies between 0 to 30 seconds. According to results from this study, memory lost from sTM within 18s.
Flashbulb memory
A memory for circumstances in which one learned of a public event, such as 9/11. These memories are not about the event itself, but about the reception event, in which one hears news about a public event.
Main reasons for forgetting long-term (episodic) memories
- Erasure/storage failure (true loss of memory content)
- Retrieval failure (memory exists but cannot be expressed)
- Memory disruption (memory is smeared or broken up)
Interference in memory
New learning “overwrites” existing memory
Decay in memory
Memory weakens over time and is eventually lost
Thorndike’s law of disuse
Hints at a process (strength is decreased), but does not suggest a mechanism. Due to his lack of a mechanism, his notion of decay has been characterized as “passive trace decay”. Attending to a memory attenuates decay.
Decay of retrieval but not storage component of memory
Two probabilities need to be considered:
1. Storage strength (indicates how well an item was learned)
2. Retrieval strength (indicates how well an item can currently be accessed).
The theory assumes that storage strength will not be reduced, and retrieval strength changes, over time, and as a function of retrieval. Over time, old memories can become less accessible because they are retrieved less often, as newer memory.
Forming memories process
Memories are made by changing the structure of synapses.
1. Learning: sending signal to change synapse
2. Forming memory: increasing number of connectors at synapse
3. Erasing memory: organized removal of added connectors (ampar) from synapse
Forgetting memories
Could require ampar removal over time. Blocking removal with peptide GluA2-3Y stops forgetting.
Retroactive interference
Forget the name of the first person you met at a party yesterday because you met five other people that night too. New memories interfere with the recall of old memories.
Proactive interference
You got a new phone number but cannot remember it well because you always recall your old one. Old memories interfere with the recall of new memories.
Availability vs Accessiblity
There is no loss of content. We fail to remember because we cannot retrieve what is stored. Information is available (stored somewhere in brain), but temporarily or permanently inaccessible (cannot be retrieved).
Role of retrieval cues in word recall procedure
Participants learned list of words from different categories. Category names preceded words, but participants were not told to remember category names. Then participants had to recall the words.
Role of retrieval cues in word recall Independent Variable
Type of recall task - free recall vs. cued recall (category names were used as cues).
Role of retrieval cues in word recall results
cued-recall group by far outperformed free recall group
Role of retrieval cues in word recall conclusion
Since the only difference was type of test administered, words were probably available in both groups. But they were much easier accessible when given the appropriate retrieval cues.
Encoding-Specificity Principle
The likelihood to recall information that has previously been encoded depends on how much the encoding and retrieval situations are similar: the higher the overlap between encoding and retrieval context, the better memory performance.
Transfer-Appropriate Processing
If the processes that are engaged to encode an item are appropriate for the retrieval task to be used to recall the item, memory performance will benefit.
Relationship between encoding processes and recall processes
Study Task: Participants were read 32 sentences. In this sentence, a word was missing. Then, after 2 seconds, they were given the missing word, which either made sense (Yes Target) or not (No Target).
Test Task: Immediately after study task, participants were given recognition test consisting of 64 items (32 targets and 32 foils).
Classes of language study
Can a child tell the difference between their native language and other languages. Example: French baby raised in France with little exposure to English and no exposure to Japanese can tell the difference between English and Japanese within a few hours of being born. If the languages are in different classes you can tell them apart right away.
Speech vs. nonspeech study
Can newborns distinguish between true speech and synthesized speech? They use high-amplitude sucking, and play a loud sound every time the newborn does a high-amplitude suck. At first they will be very willing to respond, but then due to habituation (babies habituate to this sound) the babies start to do fewer high-amplitude sucks overtime. Then, the experimenters change it to the sine wave speech, and the high-amplitude sucking will go up again, only if the baby is able to tell the difference between the sounds. Since the babies do dishabituate, it tells us they can tell the difference. This study tells us that they can tell the difference between something that’s potentially familiar (speech), and something that is definitely not familiar (sine wave speech), but its a little bit hard to know whether that’s learned or something that was built in.
Learning in the first few months - perception of sounds study
6-8 months old can tell the difference between all three different sounds, whether you are a native English speaker or not. By 10-12 months old, you lose this ability - they start ignoring the differences that are not useful in their native language. However, effect of continued exposure allows them to distinguish between different sounds that aren’t useful in your language.
The Modal Model of Memory
(external input) –> Sensory Register - (either decay then lost, or attention) -> Short term memory - (either decay then lost, or rehearsal)-> Long term memory (either decay then lost, or recall and return to stm - what happens after this step is debated). This is just a model, is not accurate of what really happens in our brain.
