Forebrain: Anatomical Organisation & Cortical Function Flashcards
Where is the cingulate gyrus?
Immediately above the corpus callosum
Outline key features of the cerebral cortex.
- outer rind of grey matter
- 40% of brain weight
What can the cerebral cortex be divided into?
1) Allocortex: comprises 3-5 layers –> divided into archicortex (most primitive) and paleocortex (includes olfactory areas such as uncus)
2) Neocortex/isocortex: consists of 6 layers that vary in thickness depending on functional localisation:
- pyramidal layers are thicker in motor areas
- granular layers are thicker in sensory areas
What is the role of motor areas?
- give rise to descending motor tracts
- if electrically stimulated, result in movement
What is the role of sensory areas?
- receive discrete inputs from sensory pathways via relays in the thalamus
- each contains a map of its sensory ‘world’
What is the concept of ‘lateralization of function’?
The idea that control areas are not always symmetrical between the two hemispheres.
Where is the primary motor area (M1)?
Precentral gyrus
What is the role of the primary motor area?
Voluntary control of muscles to the opposite half of the body
What is a lesion of the primary motor area?
- contralateral flaccid paralysis –> weakness/paralysis + reduced muscle tone) that becomes spastic (stiff) after several days
What are the two motor association areas?
Premotor cortex + supplementary motor cortex
- located anterior to precentral gyrus on frontal lobe
- responsible for complex movements + influence the movement initiated in the primary motor cortex
What is a lesion in the premotor cortex?
Form of apraxia, in which the patient is unable to perform complex movements that are guided by sensory cues e.g dressing oneself
Outline the frontal eye field.
- located anterior to the PMA
- responsible for rapid eye movements
Outline the prefrontal cortex
- governs personality, consciousness, emotional control
- located in most of the frontal love anterior to the motor areas
- responsible for problem solving, judgement, emotional/social behaviour
What is a lesion of the prefrontal cortex?
Inappropriate social behaviour, emotionally labile, poor concentration, motivation and abstract reasoning
Where is the primary somatosensory area?
Postcentral gyrus on the parietal lobe
What does the primary somatosensory area receive?
Input (e.g touch, proprioception, pain) from the contralateral side of the body via the thalamus.
What are the somatosensory association areas?
- Superior + anterior parietal lobule, separated by intraparietal sulcus
- located posterior to precentral gyrus on the parietal lobe
- responsible for integration of somatosensory information with other areas of cortex
What does the superior parietal lobule control?
- attention + visuospatial perception including manipulation of objects
- interpretation of general sensory information, consciousness of contralateral body
What does the inferior parietal lobe control?
- interpretation of emotions from facial stimuli
- interpretation of general sensory information
- language, maths, body image
Where is the primary auditory area?
- transverse temporal gyri (temporal lobe)
How is the primary auditory area tonotpically organised?
Low frequency sounds are most anterolateral and high frequency sounds are most posteromedial
Outline auditory association areas
- located lateral to primary auditory area, overlaps with Wernicke’s area
- important for interpretation of sounds
- lesion: inability to understand language, both spoken and written
Where is the primary olfactory cortex and olfactory association area?
Uncus (most anterior part of the parahippocampal gyrus which is the most inferomedial part of the temporal lobe)
Where is the primary visual area?
- located on the area surrounding the walls of the calcarine sulcus (occipital lobe)
Outline key features of the primary visual area.
- receives input from the opposite half of the visual field of both eyes via the LGN of the thalamus
- lesion of occipital lobe results in cortical blindness (a lack of conscious vision in the hemifield contralateral to the damaged hemisphere)
Where is the visual association area?
- surrounding primary visual area in occipital lobe, extends into the inferolateral part of the temporal lobe
What is the importance of the visual association area?
- important for recognition of form + colour + movement + attentional aspects of vision
- lesion –> various types of visual agnosis (ex. cant perceive colour/movement/recognise faces)
What does the insula look after?
- gustation (taste)
- located in the inferior aspect of post central gyrus, lateral fissure
What are the parts of the limbic system?
- cingulate gyrus
- parahippocampal gyrus
- hippocampus
- thalamus
- hypothalamus
- mamillary body
- amygdala
What is the limbic system important for?
Control of innate behaviours associated with survival and particularly memory
What is the uncus?
- primary olfactory cortex
- located on the anterior extremity of the parahippocampal gyrus
