Post Midterm Content Part 1 Flashcards
What is cognition?
- Cognitive functions/mental functions/high-order functions
- the things in the world reach our sensory organs and we respond through motor interactions, cognition can be defined as anything that happens “in between”
- information and recombination and transformation - mostly in the cortex
- memory, learning, attention, executive functions
What does cognition depend on?
depends on patterns of neural activity but information encoded at this level is more complex/multidimensional.
the higher up we go, the harder it is to make connectivity between the neural activity and the stimulus.
neurons in the periphery (closer to sensory organs) have a more direct correlation to the stimulus
What is the cortex?
Wrinkled, two-dimensional sheet of layered neurons
Sensory cortices
1ary and 2ary, auditory, visual, somatosensory, gustatory and olfactive
whatever gets processed in sensory organs will go up and have relays in the brain stem, the thalamus, and eventually arrive to primary sensory cortex.
For each sensory organ, we have one primary cortex (sensory cortex), part of cortex that processes sensory information.
Motor cortices
1ary motor cortex, premotor and supplementary motor (2ary)
send signals to our muscles.
3ary areas & association cortices
- the place where some of the cognitive functions are orchestrated
- regions of the cortex where injury causes cognitive deficits that cannot be explained by impairment of sensory or motor function alone.
- inputs: 1ary and 2ary sensory cortex, motor cortices, hippocampus, thalamus and brian stem.
- outputs: hippocampus, basal ganglia, cerebellum, thalamus & other cortical areas.
- have the parietal, temporal, frontal & limbic.
In terms of input, how is primary sensory areas and higher-order sensory areas different?
Primary sensory areas:
- from thalamic sensory relay nuclei
Higher-order sensory areas (V3 and V4):
- from other thalamic nuclei and lower-order areas of sensory cortex (will receive input from V1)
What is the difference between receptive fields in primary sensory areas and higher-order sensory areas?
- primary sensory areas have small receptive fields.
- higher-order sensory areas have large receptive fields.
What is the difference in arrangement between primary sensory areas and higher-order sensory areas?
Primary:
- in a precise map of the sensory receptor surface
Higher order:
- Into more imprecise maps of the array of peripheral receptors (association areas are less precise, more vague- the map starts to get lost)
What is the difference if there is an injury in the primary sensory areas, or in the higher-order sensory areas?
Primary:
- simple sensory loss
Higher-order:
- deficits of perception and cognition & intact detection of sensory stimuli
What is the difference in connectivity in primary sensory areas and higher-order sensory areas?
Primary:
- limited connections to other cortical areas (only nearby, same modality regions) (V1 is connected to V2, V3, V4)
Higher-order:
- connected to nearby unmodal areas & distal areas in frontal and limbic lobes. (V3 and V4 start connecting to association areas - start sending information to areas of brain that integrate different stimuli)
basic division of functional organization in the cortex
Information to primary sensory areas, then to secondary and third sensory areas, then association area, then motor areas, and then down.
Simplified: primary sensory areas, then higher order sensory areas, then association areas, then motor areas.
Information flow in the Nervous System
Sensory organs relay in the thalamus, send information to sensory cortices, send information back to thalamus.
Basal ganglia/cerebellum connect to the thalamus, send information to motor cortex and to muscles.
Sensory cortices send information to association cortices, through connections that go from cortex to cortex. (temporal cortex to frontal cortex - and regulate behaviour)
Association cortices are modulated by brainstem modulatory inputs.
Principles of: Information flow in the nervous system. important slide
1) Sensory information is processed serially.
2) Each area carries certain computations and conveys them to the next area, going higher in complexity and in abstraction of representation.
3) Higher-order areas project back to the lower-order areas from which they receive input. (serial - simple to complex, but the complexity will also project back)
4) Parallel pathways in each modality lead to dorsal (where) and ventral (what) association areas.
5) Goal directed motor behaviour is controlled in the frontal lobe.
What is the difference in flow of information for the sensory stream and the motor stream?
The motor stream is descending, and the sensory stream is ascending. (these happen at the same time)
For every pathway that goes up, there is a pathway that goes down (bottom-up and top-down)
How are functional areas in the cortex organized? What are the principles?
1) Structure.
2) Physiological response.
3) Connectivity.
Principles:
1) all areas fall into a few functional categories. (sensory, motor, association)
2) areas in a category occupy a discrete continuous portion of the cortical sheet. (one portion that we can identify that has common characteristic and perform specific function)
3) areas that are functionally related occupy neighbouring sites. (if two areas do the same thing, they have to be connected)
Cortical structure (Lamination)
- we have different types of cortex!
- neocortex, paleocortex (piriform) and archicortex.
- cognition: we talk mostly about neocortex.
- areas around the hippocampus are the archicortex (and has 4 layers)
- piriform cortex (related to memory and olfaction - in many organisms beyond humans, has 3 layers)
- neocortex has 6 layers, some layers have neurons and some are dendrites.
- each level has different density of cell bodies, density of dendrites, discover by cutting and looking at a microscope.
Cortical structure: Canonical circuit
1) Each layer has a primary source of inputs and a primary output target. (benefit to having 6 layers of neurons - organization of information)
2) Connections in the vertical axis (columnar or radial connections)
3) Connections in the horizontal axis (lateral or horizontal)
4) Cells with similar functions arranged in radially aligned groups.
5) Interneurons within layers give rise to axons that extend horizontally (linking functionally similar groups) (may be inhibitory - link neurons in different layers)
Cortical organization: Regional variation
1) Korbinian Brodmann, cut the brain sliced it in every spot and made a map. He saw cytoarchitectural areas and draw that map. This was before there was fMRI. “regions of the brain with similar structures in. both cell type layering could produce a specific function” (gradient - cells start changing from one area to another)
2) Eventually…using histological staining techniques showed us cortical organization:
- cell density, cell size
- cortical thickness
-laminar size
—> the way we see the 6 layers of neocortex, is different from how we see it in visual cortex, motor cortex, etc.
-> the organization is not just related to structure but it is to function as well.
What experiments confirmed brodmanns thinking of the cortical organization having regional variation?
1) Neurological case studies
- Broca & Wernicke - language of phinease Cage - PFC Brenda Milner - memory.
2) In-vivo electrophysiology in animals
- Decision making and reward - PFC.
3) Neurosurgical patients
- Wilder Penfield and the motor and sensory homunculi.
What are modern neuroscience studies in humans?
1) Neurophysiological testing
2) Functional neuroimaging & Neuromodulation (temporarily activate or inhibit an area of the brain with pulses) combined with psychological tasks.
3) Lesion studies.
Ex. memorize this set of cards, record brain activity.
See the areas of brain that are active.
-> can map function to structure.
What are unique features of association cortices?
1) Primary sensory cortices receive information from particular thalamic nuclei, lateral geniculate, medial geniculate.. association cortices will not receive most of their information/directly from the thalamus.
2) Some information that arrives from the thalamus has already been processed by sensory and motor areas.
3) Majority of input to association cortices come from corticocortical connections (other cortical areas communication)
-» Same hemisphere - U shaped fibres/long association fibres. (connect temporal to frontal example)
-»> Interhemisphere- long association through corpus callosum.
What are association cortices modulated by?
- by subcortical nuclei (important source of innervation)
1) Cholinergic - brainstem and basal forebrain - memory, learning, attention (helps do cognitive activities)
2) Dopaminergic - midbrain - pleasure salience, motivation, reward-learning (linked to anticipation of pleasure/motivation)
3) Noradrenergic - brainstem - wakefulness, stress reaction (activator)
4) Serotoninergic - brainstem - mood, memory processing, sleep. (emotional states)
all association areas receive different neurotransmitters from the brain stem.
Cholinergic
memory, learning, attention (helps do cognitive activities)
Dopaminergic
pleasure salience, motivation, reward-learning (linked to anticipation of pleasure/motivation)
Noradrenergic
wakefulness, stress reaction (activator)
Serotoninergic
mood, memory processing, sleep. (emotional states)
What does each association area have?
- a distinct set of subcortical connections
- has very own particular pattern of connections that go to different areas
- different within every human because we have all had different experiences
Ex. musicians have higher connectivity have higher association between motor coordination (hands) and auditory (music)
What is the functional specialization of the association area in the Parietal lobe?
- attention & perceptual awareness of body and stimuli around it
- integrates somatic, visual, acoustic and vestibular sensory information - spatial cognition and motor control of the eyes and extremities.
- the most anterior (more to front) part of the parietal cortex is the somatosensory cortex. So the first thing we encounter is the somatosensory cortex, then in the back, it stops where the visual cortex starts. It is also close to the auditory cortex (because that is in the superior part of the temporal lobe) = multisensory integration (integrates the 3 of them)
- linked to the where pathway (locates things in space)
What is the functional specialization of the association area in the Temporal lobe?
- categorization, object recognition, semantic memory (language comprehension)
- Lateral - auditory association cortices - including Wernicke’s area (language comprehension are)
- Ventral - WHAT pathway - recognition of sensory stimuli - faces/words/objects - lesion: AGNOSIA (cannot recognize what we are presented with, but we can see it and we can describe it) - do not know what it is.
- if more apperceptive (more posterior) : cannot copy.
- if more associative (more anterior) : cannot associate objects (but can perfectly copy it)
- strong connection to the limbic system - emotion & memory (amygdala and hippocampus)
What is the functional specialization of the association area in the Frontal lobe?
- planning & regulation of behavior (decision making and behavioural inhibition)
- largest lobe/widespread connectivity/most complex functional anatomy
- integrates information from sensory & motor cortices, parietal & temporal association cortices.
- appreciation of self in relation to the world - allows selection, planning and execution of appropriate behaviour (social contexts)
- damage in the frontal lobe - change in “character” or “personality”
- short term memory functions and planning - more dorsolateraly
- value and decision making - more ventromedially
How did we discover that there was attention sensitive neurons?
- we have attention sensitive neurons in the parietal cortex.
1) have monkey that pays attention to different things, manipulate what it pays attention to with a reward and a stimulus appears, the monkey is very attentive to it, we record from parietal cortex and see that the neurons fire.
2) people listening to words, count the amount of times we hear the word STAR among random words. Waiting for the word star, paying attention to star. Record the activity starting each word. Saw that when it was STAR the parietal lobe showed WAY more activity.
Contalateral hemineglect syndrome
- Lesions in the right parietal lobe impair spatial awareness! -> leading to an inability to attend to stimuli on the left side.
- This suggests the right hemisphere’s dominance in processing spatial information and integrating sensory inputs from both sides of the body.
- Lesions in the left parietal lobe do not produce the same attentional deficit, indicating that the right hemisphere plays a crucial role in attending to stimuli from both sides, while the left hemisphere predominantly attends to the right side.
- Role in Spatial Awareness (lateralized to the right)
- Important role in multimodal/sensorimotor integration
Case of Phineas Gage
- frontal association cortex
- functional deficits: cognitive disabilities, impaired restraint, disordered thought, perseveration and inability to plan appropriate action.
- Phineas gage became inconsiderate, intemperate etc.
- Joe A showed little restraint, lost initiative and creativity
- Frontal lobotomies
Limbic association cortex
- at the edge of the cortical surface, medial view of the hemispheres
- orbital and ventromedial cortex - connected to amygdala and hippocampus - emotional processes
The Circadian Cycle
The circadian rhythm, which governs physical, mental, and behavioral changes, follows a cycle influenced by external cues like light and daily routines. These changes include variations in alertness, mood, and activity levels.
External cues such as light, meal times, and social interactions help distinguish between day and night, regulating our cortical state of being awake or asleep. However, the duration of this cycle can vary from person to person. In an experiment, when external cues were removed, the circadian rhythm of a participant shifted by approximately 2 hours every day, indicating an intrinsic cycle length of 26 hours. When gave the person cues back, the cycle readjusted back to normal.
External cues regulate our cycle (how important light is and other routines)
What are visceral functions regulated by?
- they are regulated by the hypothalamus and the visceral nervous system
- hypothalamus is a structure that has a series of nuclei that will be important for regulating our hormonal states or visceral functions. Sends signals down different mechanisms to regulate.
Circadian rhythms
1) Internal or biological clock
- encoded in our genes
- homeostatic regulation
- temperature, levels of hormones (GH, cortisol)
- operates even in absense of external information
- hypothalamus (suprachiasmatic nucleus), adrenal glands
Regulation by environmental information:(associated with better physical and mental health)
1) Light (to fit day/night cycle)
-> sensors in the retina signal changes to the brain (hypothalamus - SCN - central or MASTER clock)
2) Physical activity
-> increased temperature and metabolism (muscle tissue and other organs - peripheral cloc)
Cortisol
1) Hormone associated to stress - Peaks happen in the morning (when you wake up) - 6am
2) opposite to melatonin
3) Periodic secretion is controlled by the circadian clock (central pacemaker 0SCN and adrenal gland clock)
4) plays a part in the synchronization of the cell-autonomous clocks
5) increased secretion with:
- immune system response, intense physical activity, physiological and emotional stress.
Melatonin
Hormone that peaks at 3 or 4am when you are in deep sleep
when does growth hormone peak?
Growth hormone peaks at night, we do important growing during our sleep.
Regulation of circadian rhythms by light
- sensors in the retina that will signal changes in light to our hypothalamus, and then this will regulate different hormones that we can release during the night or the day.
1) Intrinsically photosensitive ganglion cells - MELANOPSIN (sensitive to degree of light - when a lot of light, these cells are inhibited, when there is not, they are activated)
2) (hypothalamus) Suprachiasmatic nucleus “master clock” or pacemaker. (receives input from the retina)
3) Pineal gland - synthesizes MELATONIN.
Cyrcadian effects on learning and mood
- seasonal effective disorder “winter blues”
- less light in winter so the circadian rhythms are not regulated anymore.
- there is another pathway, that connects the photosensitive ganglion cells in the retina, directly to brain areas linked to emotion. (not only important to regulate circadian rhythms, it is also important to regulate mood)
What is the behaviour description of sleep?
- reversible state of perceptual disengagement from and unresponsiveness to the environment
- postural recumbence, behavioural quiescence, closed eyes
- “normal suspension of consciousness”
What are the sleep requirement’s?
“a series of controlled physiological states governed by a group of brainstem nuclei” - restorative effect.
- requirements: 7-8 hours per day
- varies among individuals, varies with age. (at birth you need many more hours of sleep and this number goes down as you get older) (older people need less hours of sleep - requirements start getting smaller and smaller)
