Exam 1 Flashcards
What factors shape our perception?
- Our genetic makeup
- The epigenetic environment in which we develop
- Our experiences
illusion
A mistake in perception that happens when the brain misinterprets a stimulus, causing us to perceive things in a way that is different from the actual stimulus. Our brain relies on our experience to make predictions, but sometimes gets it wrong. Differ from hallucinations, daydreams, etc. because it is based on an ACTUAL stimulus.
perception
The processing and interpretation of information acquired by sensory systems
sensory system (and basic parts)
Any body system that transduces energy from the environment into patterns of neural impulses. They all include an organ that collects energy from the environment, receptor cells that capture that energy and transduce it into neural signals, afferent nerves to transport the signal, and brain circuitry to process it.
transduction
To change from one energy form to another. In sensory systems, it’s a change from environmental stimulus energy (light, chemical odorants, sound waves, etc.) to neural impulses (chemical and electrical signals)
What are the main parts of the central nervous system?
Brain and spinal cord
nucleus (in terms of gross anatomical structure)
a spatially segregated group of neurons with related function, located within the central nervous system
ganglion
a spatially segregated group of neurons with related function, located in the peripheral nervous system
cranial nerves
nerves that emerge directly from the brain
spinal nerves
nerves that emerge from the spinal cord
sensory vs motor nerves
Sensory neurons carry signals from the outer parts of your body (periphery) into the central nervous system. Motor neurons (motoneurons) carry signals from the central nervous system to the outer parts (muscles, skin, glands) of your body.
glial cells
supporting cells that surround neurons
What are ions and their role in the nervous system?
Ions are charged chemical particles. They are important in creating membrane potentials, which serve as transmission of a signal along neurons.
What ions are found inside and outside neurons?
Na + outside the cell (rushes in during AP), K+ inside cell (rushes out during AP)
Describe the flow of ions and changes in electrical potential that occur during the action potential
First, voltage-gated sodium (Na+) channels open, allowing Na+ to rush from the extracellular space into the cell, causing the interior of the cell to become even less negative with respect to the outside. At some point, the membrane potential actually becomes positive instead of negative. When the membrane potential becomes positive enough, the voltage-gated Na+ channels are inactivated and Na+ no longer enters the cell. At this point, voltage-gated K+ channels open, K+ rushes out of the cell, and the membrane potential becomes negative again (repolarizes). The rapid efflux of K+ from the cell causes a slight undershoot (hyperpolarization).
action potential
A rapid reversal of membrane potential, needs enough energy to meet the threshold to start
EPSPs and IPSPs
Graded potentials caused by different amounts of NT influx.
Excitatory post-synaptic potential: a depolarization caused by excitatory neurotransmitters that makes an AP more likely
Inhibitory post-synaptic potential: a hyperpolarization caused by inhibitory neurotransmitters that makes an AP less likely
ligand-gated ion channels
Ion channels that open/close based on the binding of chemicals.
voltage-gated ion channels
Ion channels that open/close based on voltage of the membrane potential
absolute refractory period of a neuron
The period during which another action potential cannot be generated under any circumstances
relative refractory period of a neuron
The period during which extra depolarizing current (an extra large EPSP) is needed to generate an action potential.
neurotransmitters
Excitatory: Glutamate, acetylcholine
Inhibitory: GABA, glycine
depolarization
When the inside of a cell becomes more positive relative to the outside of a cell
hyperpolarization
When the inside of the cell re-polarizes and becomes negative relative to the outside again, it overshoots a little and becomes even more negative than it was originally, for a short time
spatial summation
Occurs when an individual neuron receives simultaneous inputs from multiple sources. The small EPSPs contributed by many different synaptic terminals add up to produce a single large EPSP that may be sufficiently large to reach threshold.
temporal summation
Occurs due to the fact that every postsynaptic potential has a finite time-course, usually lasting at least several milliseconds. This means that if a second input arrives before the EPSP or IPSP elicited by the previous one has finished, the two can add together
convergence in neural circuits
Output from many neurons onto one. Many different presynaptic neurons provide input to a single postsynaptic neuron. These inputs may be excitatory or inhibitory, and may be active at different times.
divergence in neural circuits
Output from one neuron onto many. Each postsynaptic neuron receives input from the same presynaptic neuron, but may react to it differently.
How is information about the environment represented by neurons?
In spatio-temporal patterns of neural activity involving electro-chemical signals
What kinds of changes can occur in the brain of an adult (for example, as a result of learning)?
Reinforcing or weakening synapses between certain neurons; dying neurons; forming new synapses
How is information about taste and smell represented in patterns of neural activity?
spatio-temporal patterns
Where are the first neurons in the olfactory system located?
The olfactory receptor cells, which are true neurons, are located in the olfactory epithelium
How does experience early in life influence brain development?
Can influence which genes are expressed, resulting in different amounts of receptors, etc. Injury can also influence development.
psychophysics
The systematic study of the relationship between the physical properties of a stimulus in the environment and the perception of that stimulus
absolute threshold and how to measure
The smallest amount of stimulus energy that can be detected by an observer at an above-chance level (>50% of the time). Measure with method of limits, adjustment, or constant stimuli
Weber’s law
JND is a fixed percentage of the reference stimulus: ΔI/I =K, where ΔI is the difference between the reference and comparison stimulus, I is the reference stimulus, K is the Weber constant
JND threshold
Just Noticeable Difference threshold is the smallest detectable difference between 2 stimuli
magnitude estimation
What’s the relationship between different values of the stimulus (ie different volumes) and what we perceive?
method of limits
In this method, stimuli of different magnitude are presented in either ascending or descending order by the experimenter and subjects are asked to indicate whether or not they detect the stimulus.
method of adjustment
A variation of the method of limits; in this method, the subjects rather than the experimenter control the magnitude of the stimulus and are asked to adjust it up until they can perceive it, or to adjust it down until it disappears.
method of constant stimuli
In this method, stimuli are presented by the experimenter in random order and subjects are asked whether they can detect the stimulus. Reduces effect of expectation/adaptation
errors that can occur when measuring absolute threshold
Expectation of pattern, adaptation to the stimulus, self-report is inconsistent
response compression
?
response expansion
?
transduction basic steps
- Stimulus energy must reach receptor cells
- Receptor cells activated
- Receptor potential
- Release of NT to the primary afferent nerve
Describe the basic flow of information in most sensory systems, starting with an external stimulus and ending in the cerebral cortex
external stimulus → receptor cells → ganglion or nerve → processing in periphery or brainstem→ thalamus → cortex
The chemical senses include…
Smell, taste, oxygen/CO2 level detection in blood, lactic acid detection in muscles, irritant detection in skin
taste receptor cells
Constantly dying and being replaced. Grouped in taste buds. Have microvilli that reach the taste pore and contact food particles, connected to nerves. Each cell typically has mechanisms for sensing multiple classes of substances.
transduction in taste receptor cells
The membrane of every taste receptor cell contains ion channels and/or G-protein-associated receptors for specific molecules or groups of molecules. When molecules bind or pass through, a receptor potential is generated. Salty/sour molecules are small and can pass down their gradients thru ion channels. Bitter/sweet/umami molecules are bigger and bind to receptor sites, that cause ion channels to open. The receptor cell then releases NTs (mostly glutamate) to the next cells.
Spatio-temporal patterns
Patterns in both the population (spatio) of neurons active, and in the timing (temporal) of the activity combine to convey information about stimulus qualities
What is the first structure in the brain that receives information about taste?
nucleus of the solitary tract (NTS)
Where are the first neurons in the olfactory system located?
The olfactory receptor cells, which are true neurons, are located in the olfactory epithelium
conditioned taste aversion
a specific taste paired with nausea/some other noxious stimulus, leaves a lasting aversion to the taste. Most likely to develop w novel stimuli
olfactory pathway
olfactory epithelium –> olfactory bulb –> primary olfactory cortex –> thalamus –> orbitofrontal cortex (the ONLY pathway that synapses in the cortex before the thalamus)
taste pathway
tongue –> nucleus of the solitary tract (brainstem) –> thalamus –> cortex
modality specificity
When a sensory system is specialized for one type of energy input/stimulus (i.e. olfactory system is specialized to receive chemical inputs, won’t respond to acoustic signals)
gustation
Taste. Involves molecules in solids and liquids that are water-soluble, begins on tongue
olfaction
Smell. Involves molecules in the air that are lipid-soluble and volatile, begins in nose
In what ways are the systems for olfaction and taste similar? In what ways are they different?
Similar: chemical senses, closely related to survival drives
Different: Smell goes to cortex before going to thalamus, unlike other systems; olfactory receptor cells are true neurons, sense different types of molecules, begin in different places
What features do the chemical senses have in common with all other sensory systems? In what ways are they different?
Similar: Transduction, adaptive, take info from the environment, organs that collect the energy
Different: Chemical senses are ancient, closely linked with basic drives, sometimes used for cellular communication (hormones etc), and deal w stimuli whose structures have no direct relationship with our perception of the stimuli
neurobiology
The study of the structure and function of brain systems. Can be at the gross anatomical level, microscopic level, or connections level
extracellular neural recording
Recording neural activity when the electrode is placed outside and very near the neuron. Records voltage changes on the outer membrane of the cell, less invasive than intracellular recording
intracellular neural recording
Recording neural activity when the electrode is placed inside the neuron, and a reference electrode is on the outside. Records voltage changes across the cell membrane, more invasive
electroencephalogram (EEG)
A method for recording many neurons at once. Records the algebraic sum of all types of activity in many neurons. Waveforms depend on synchronized activity of the same sign (positive or negative)
functional imaging
A method for recording many neurons at once. Uses an indirect method, like blood flow, to draw conclusions about how much metabolic activity is occurring in different parts of the brain
computer-aided tomography (CAT)
A method for recording many neurons at once. 3D reconstructions of x-ray images
magnetic resonance imaging (MRI)
A method for recording many neurons at once. Measures magnetic properties, which differs across tissue types.
functional magnetic resonance imaging (fMRI)
A method for recording many neurons at once. Measures magnetic properties of hemoglobin in different states, providing an indirect measure of blood flow
receptor potential
A graded change of a receptor cell’s membrane potential. Size of the receptor potential depends on amount of stimulus energy and the size of the potential influences how much neurotransmitter the receptor cell will release.
graded potential
Changes in membrane potential that change in voltage depending on the amount of input of either stimulus energy (receptor potentials) or neurotransmitters received (EPSPs/IPSPs)
adaptation
Continuous stimulation leads to a decrement in perceived intensity. Typically, sensory neurons fire most at the stimulus onset. During the remainder of the stimulus, firing rate decreases, or the neuron may stop firing entirely. Adaptation may persist after the stimulus is gone.
short-term adaptation
Occurs in response to an ongoing stimulus, but is quickly reversed when that stimulus is no longer present. Caused by saturation of receptor sites, or ion equilibrium being reached across the membrane.
long-term adaptation
Occurs with repeated exposure to a stimulus. A commonly encountered stimulus no longer elicits a response or attracts attention. Caused by CNS “gating” processes that block incoming info, or by peripheral processes like the slow-down of certain receptor sites.
cross-adaptation
If adaptation has already occurred to one stimulus, a similar stimulus may also appear as less intense than if the adaptation had not occurred. The more similar the stimuli, the more transduction mechanisms they will share.
receptor cell threshold
The point (in stimulus energy input) at which the receptor cell responds, such as by releasing NTs
dynamic range of a receptor cell
The range of stimulus values over which a change in stimulus magnitude elicits a change in response. Starts at the threshold and ends at the point where there is no more change in membrane potential (asymptote)
What contributes to taste (beyond info relayed to taste receptor cells)?
Astringent sensations from things like peppers, texture, temperature, olfaction, visual appearance, what and whether we’ve already eaten
papillae
Bumps on the tongue that contain the taste buds. Fungiform at the tip, foliate on sides, circumvallate at the back .
taste bud
Structures in the papillae made up of groups of taste receptor cells. Has a taste pore opening at the top, and is contacted by afferent nerve fibers.
How is are taste and olfaction represented in neural activity?
A spatio-temporal pattern of different groups of neurons activating at different times to code for all different tastes and smells.
olfactory epithelium
Structure on the roof of the nasal cavity which contains the olfactory receptor cells, supporting cells, and axons that lead to the olfactory bulb.
olfactory mucus
Mucus on the olfactory epithelium that contains protein molecules that pick up odorant molecules and transport them to receptor sites on the cilia
olfactory receptor cells
The sensory receptors for the olfactory system. Located on olfactory epithelium. True neurons that create AP’s. Die and are replaced every 5-8 weeks. Cilia on their dendrites stick out into the olfactory mucus to bind odorants. Each has only one type of receptor protein
transduction in olfactory receptor cells
When odorants bind to the cilia of the receptor cells’ dendrites, a receptor potential is created in the dendrites. This becomes an EPSP at the cell body, and finally an action potential in the axon.
2-alternative forced choice method
A method for measuring absolute threshold. A stimulus is presented at one of two locations (the other location has no stimulus).
The level of the stimulus is randomly varied to determine the level at which it is detectable 50% of the time. The subject must choose the location at which the stimulus is present. An objective method that can be used with animals, infants, or hard-to-test subjects.
catch trials
Trials on which no stimulus is present. If the subject is guessing, he will say “yes” on about 50% of these trials
