Cognitive functions and the organization of the cerebral cortex Flashcards
True or false: cognitive functions are a part of the lower order functions?
False: cognitive functions are a part of the higher-order functions and sensory functions lower order
Cognition can be defined as….
Anything that happens “in between’: information recombination and transformation, mostly in the cortex.
What is included in cognition and how is the info encoded?
Memory learning attention executive functions "Consciousness" Info is coded in a more complex/multidimensional
Where is cognition encoded in the brain and what are the inputs and the outputs?
-in the cortex: a wrinkled, 2-dimensional sheet of layered neurons
-Input:
➳-Sensory cortices: primary and secondary for auditory, visual, somatosensory, gustatory, and olfactive
➳Motor cortices: primary motor cortex, premotor and secondary motor
➳hippocampus, thalamus, and brainstem
-Outputs:
➳hippocampus, basal ganglia, cerebellum, thalamus and other cortical areas
What is the role of the tertiary areas in the cortex and what would happen if they are lesioned?
They are association cortices: unimodal and multimodal
“regions of cortex where injury causes cognitive deficits that can not be explained by impairment of sensory or motor function alone”
What are the differences between primary sensory areas and higher sensory areas?
➳Primary sensory areas : Receive input from thalamic sensory relay nuclei
Higher order sensory areas: Receive input from other thalamic nuclei and lower order areas if sensory cortex
➳Primary sensory areas : Small receptive fields
Higher order sensory areas: thicc receptive fields
➳Primary sensory areas : Arrangement into precise map of the sensory receptor surface
Higher-order sensory areas: Organized into more imprecise maps of the array of peripheral receptors
➳Primary sensory areas : Injury: simple sensory loss
Higher-order sensory areas: Injury: deficits of perception and cognition & intact detection of sensory stimuli
➳Primary sensory areas : Limited connections to other cortical areas: only nearby, same modality neurons
Higher-order sensory areas: Connected to nearby unmodal areas & distal areas in frontal and limbic lobes
Information flow in the nervous system
- Sensory information is processed serially
- Each area carries certain computations and conveys them to the next area, going higher in complexity and in abstraction of representation
- Higher-order areas project back to the lower-order areas from which they receive input.
- Parallel pathways in each modality lead to dorsal and ventral association áreas
- Goal directed motor behavior is controlled in the frontal lobe.
Principles for the organization of functional areas in the cortex
1) all areas fall into a few functional categories
2) areas in a category occupy a discrete, continuous portion of the cortical sheet
3) areas that are functionally related occupy neighboring sites
Number of layers in paleocortex, neocortex and archicortex aka hippocampus
Paleocortex: 3
Neocortex :6
Archicortex aka hippocampus: 4
Cortical structure: canonical circuit
- Each layer has a primary source of inputs and a primary output target
- Connections in the vertical axis (columnar or radial connections)
- Connections in the horizontal axis (lateral or horizontal)
- Cells with similar function arranged in radiallyalignedgroups
- Interneurons within layers give rise to axons that extend horizontally (linking functionally similar groups)
True or false: the regions in the cortex are very clear and what helps delimitate them?
False: they are gradients: 52 distinct cytoarchitectural areas -Cortical organization: ➳Cell density, cell size ➳Cortical thickness ➳Laminar size
How did we know that the different areas of the cortex were also functionally distinct?
- They studied neurological cases like Phineas Gage
- EEGs in animals
- They studied neurosurgical pateints
Modern cogsci/neuroscience studies in humans
- Neuropsychological testing: like the memory cards because you can test lots of skills
- Functional neuroimaging combined with psychological tasks
- Neuromodulation (magnetic pulse to activate or inhibit a spot in the brain) combined with psychological tasks
Unique features of association cortices
- Thalamic nuclei:
pulvinar –parietal association medial dorsal
–frontal association - Information that arrives from the thalamus has already been processed by sensory and motor áreas
- Majority of input is from corticocortical connections
same hemisphere–U shaped fibers/ long association fibers
interhemispheric–long association through corpus callosum
“Segregated columns that interdigitate inter-hemispheric with ipsilateral projections
What is the subcortical nuclei important for?
Important source of innervation
association cortices are modified thanks to it
What are cholinergic neurons important for and where do they synapse?
- Brainstem, basal, forebrain
- memory, learning and attention
What are dopaminergic neurons important for and where where do they synapse??
midbrain
–pleasure, salience, motivation, reward-learning
What are noradrenergic neurons important for and where do they synapse?
–brainstem
wakefulness, stress reaction
What are serotoninergic neurons important for and where do they synapse?
–brainstem
–mood, memory processing, sleep
“Each association area is defined by a …..
“Each association area is defined by a distinct, if overlapping, subset of thalamic, corticocortical and subcortical connections”
Functional specialization of association areas:
- Parietal –attention & perceptual awareness
- Temporal –Categorization, recognition, semantic memory
- Frontal –planning & regulation of behavior (decision making and behavioral inhibition)
Parietal association cortex: what does it do?
- Attention and awareness of the body and stimuli around it
- Integrates somatic, visual, acoustic, and vestibular sensory information -spatial cognition and motor control of the eyes and the extremities.
Where does the IPS project do ?
projects to: the premotor area ➳the frontal eye fields ➳prefrontal area -controls: ➳ocular movements ➳ reaching and grasping of the upper extremities ➳spatial working memory
Inferior parietal lobule and precuneus project to …. and what does it do?
Inferior parietal lobule and precuneus project to the parahippocampal and entorhinal cortices
-strongly associated with hippocampal functions for long-term memory formation
What is a disease that can happen because of a lesion in the parietal association cortex?
•Contralateral neglect syndrome–role in spatial awareness
•Attention sensitive neurons
-Important role in multimodal/sensorimotor integration
-Usually on the left because the right side can usually do a little bit of left, so if right is lost then you are in deep trouble
What is in the temporal association cortex?
- Auditoryassociationcortices–including Wernickes(language-comprehension area)
- Ventral –WHAT-pathway –recognition of sensory stimuli –faces/words / objects
- Representation of knowledge –Semantic memory -meaning
- Strong connection to the limbic system.
What happens when there is a problem in the temporal association cortex?
it is usually important for recognition
Ventral/Inferior temporal surface(“What” pathway) –Agnosia
➳specific type of stimuli according to región.
➳More anterior: associative// More posterior: Apperceptive
-Anterior pole –Semanticdementia–cannot associate words with their meanings (fluent aphasia, anomia, impaired comprehension of word meaning, and associative visual agnosia)
Prosopagnosia and alexia not sure about this one
Prosopagnosia
- Can’t recognize faces
- usually in right temporal lobe
- these things happen tp the right because of language and facial recognition happens more to the right
alexia
“alexia” –Visual Word Form Area(VWFA)left temporal lobe
Frontal association cortex
- last one to develop
- helps us to follow social rules
- Largest lobe/widespread connectivity/ most complex functional anatomy
- Integrates information from sensory & motor cortices, and parietal & temporal association cortices.
- Appreciation of self in relation to the world–allows selection, planning, and execution of appropriate behavior (social contexts)
- Damage in the frontal lobe –change in “character“ or “personality”
Frontal association cortex: functional deficits, examples and main cause:
-Cognitive disabilities
- impair restraint
-disordered thought
-perseveration
-inability to plan appropriate action.
•Phineas Gage–Became“inconsiderate, intemperate, could not cope with normal social intercourse nor practical planning”.
•Joe A –“showed little restraint, was unable to match the appropriateness of what he said, lostability to plan for the future, lost initiative and creativity”
•Usually because of Frontal lobotomies
Limbic association cortex
At the edge of the cortical surface, the medial view of the hemispheres
•It used to be understood as a unitary system“the limbic lobe” :homeostatic and instinctual drives
•Orbital and ventromedial cortex–connected to amygdala and hippocampus: emotional processes
•Hippocampal formation–mediates the formation of long-term memories and then transfers them to the neocortex.
•Otherdivisions–intermediaries between hippocampal formation and association cortices
True or false: the frontal association cortex is working on short term memory
True: short term memory functions and planning more dorsolateraly
True or falseL value (subjective to what you like more) and decision making is made more laterally:
FALSE: it is more ventromedially
“used remembered info to plan and guide appropriate sequences of behavior”
Functional specialization of association areas: key points
- Areasare NOT separate modules -gradient
- They are organized into large, denselyi interconnected networks that function together→LARGE SCALE BRAIN NETWORKS
- Within these NETWORKS, there are hierarchical organization.
- As areas goup in hierarchy, information is more abstract and distant from peripheral sensors. (think primary visual cortexes. Temporal association cortices)
