T8 (Fys) Fallet M.H. Flashcards
What is the idea of the canonical neocortal circuitry?
It communicates the idea that there is a certain pattern of input and output for each area of the association cortex.
- a main input area, and output target
- radial and horizontal connections
- cells of similar function arranged radially, spanning all cortical layers
- extensive local axons link similarly functioning columns of cells
What are cytiarchitectonic areas?
The different regions of the association cortices, where difference is observed in the relative thickness and organization of the different cellular layers.
How does the input from the thalamic nuclei to the association cortex differ from that received by the primary sensory cortices?
The information reaching the association cortex from the thalamus originates from the primary motor and somatic sensory cortex, and has thus been processed once already.
What connections are the greatest source of input to the association cortex?
Corticocortical connections. These include:
- ipsilaterally: primary and secondary motor/sensory cortex, other association cortices
- contralaterally: interhemispheric (via corpus callosum) connections including corresponding and non-corresponding areas of the hemisphere
What is the main laminar difference between the hippocampus and the neocortex?
Yhere are only 4 laminae whilst the rest of the cortex generally contains 6. The hippocampus is thus termed the archicortex, signifying an earlier historical appearance.
What subcortical inputs does the association cortex receive?
- dopaminergic nuclei in midbrain
- noradrenergic amd serotonergic nuclei in brainstem reticular formation
- cholinergic nuclei in brainstem and basal forebrain
What is contralateral neglect syndrome?
The inability of perceiving or understanding one lateral side of the oneself and one’s surrounding (or even one side of single objects), following damage to the contralateral parietal lobe (motor deficits termed ‘apraxias’).
How do you explain contralateral neglect syndrome arising mainly from lesions of the rigt parietal lobe, as opposed to the left?
There lies a hemispheric bias to observation of ones surroundings. Whilst the left hemisphere usually specializes in language processing, the right hemisphere is allocated to observing both right and left reality. Whilst the left hemisphere may also observe the right hand reality, there is no such double-safe available for the left-hand field.
What is Balint’s syndrome and what does it tell us about the parietal cortex?
Balint’s syndrome usually follows a more dorsal or medial lesion to the parietal cortex. Three symptoms follow:
- Simultanagnosia: inability of perceiving a complex visual field as a whole
- Optic ataxia: deficits in visually guided reaching
- Ocular apraxia: difficulty in voluntary scanning of the visual field
Understanding of instructions in other than visual form however continue to be unimpaired.
These symptoms suggest that the parietal lobe is important for constructing spatial awareness for guiding attentiion as well as movement.
What measurable difference in the parietal cortex is observed when the subject is attentive vs. unattentive to some stimulus?
Single neuron activation increases, indicating the function of the parietal cortex in coordinating attention to the left- and right-hand field.
How does an agnosia differ from neglect syndrome?
A person with agnosia is able to report and respond to a stimulus but unable to say what or where it is, whereas neglect syndrome entails total ingorance of the stimulus, apart from reacting to it (e.g. flexion reflex still works).
What might result from damage to the temporal association cortex?
Prosopagnosia, inability to remember or discern faces. One can still describe and identify facial features, but not the face as a whole.
What does the existence of temporal cortical patches responding to certain facial features tell us?
The relative importance for humans to recognize others’ facial expressions.
How are faces and objects generally recognized by the temporal lobe neurons?
Specific neurons/columns react to specific facial features and orientations (profile vs. front). Furthermore there are specific neurons/columns for specific shapes, meaning complex shape recognition is a common effort by multiple neurons each recognizing specific parts kf the shape.
In what way does the prefrontal cortex guide behaviour associated with learned behaviour?
Planning neurons near the principle sulcus are coded to fire in a specific order following certain cues and utilizing e.g. delay-specific neurons. This lets the person/monkey repeat a given behaviour and maintain the activity despite intermittent pauses (as long as they are part of the movement).
