Chapter 7 part 2 Flashcards
prefrontal cortex
- areas of the frontal lobe located anterior the motor functional areas (i.e., 4, 6, and 8)
- outputs to SMA and PMC
- active when planning behaviors
- active when new motor skills are being acquired
- includes areas that mediate higher mental functions
- language areas located here: Broca’s area (areas 44 and 45)
major divisions of the prefrontal cortex
dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC), anterior prefrontal cortex (APFC) (frontal pole), medial prefrontal cortex (MPFC) (ventromedial prefrontal cortex)
medial prefrontal cortex (MPFC) or ventromedial prefrontal cortex
- important in decision-making
- houses orbitofrontal cortex
lesions on lateral side of prefrontal cortex leads to…
- varying degrees of working memory deficits (verbal or non-verbal)
- executive function deficits: poor inhibitory control, poor reasoning and problem solving; poor planning
- varying degrees of transcortical motor aphasia: similar to Broca’s, but different from it in that repetition is intact
other functions in frontal lobes
the tongue and taste system; olfactory system
taste pathway
- signal begins when a taste cell responds to a tastant
- 3 cranial nerves (7, 9, 10) carry signals to medulla via nuclear solitary tract (NST)
- from NST, some fibers go directly to thalamus and some go to limbic regions (e.g., amygdala)
- from thalamus signals go to insula and gustatory areas, which are also in frontal lobes
- from there, neurons reach also the orbitofrontal cortex
orbitofrontal cortex
thought to be involved in processing the reward value of food and the resulting motivation to eat food
five basic tastes
salt, sour, bitter, sweet, and umami
olfactory system
- transduction from odor to neural signal begins when the odorant attaches to a receptor in the olfactory epithelium
- signal is transmitted to olfactory bulb through tiny olfactory nerves that pass through holes of a bone (cribiform plate)
olfactory bulb relays signals to…
- primary olfactory cortex –> detect a change in external odor
- orbitofrontal cortex (secondary olfactory cortex) –> identifying smell
key functions in occipital lobe
primary visual cortex; “what” and “where” pathways
primary visual cortex
- area 17
- primary recognition of visual stimuli
- surrounding it in the occipital lobe is the association visual cortex
optic chiasm
- 50% cross: those from medial half of retina
- 50% do not cross: those from lateral half of retina
optic pathway
optic nerve –> optic chiasm –> optic tract –> synapse at lateral geniculate nucleus –> courses as optic radiations –> primary visual cortex
somatotopy of occipital lobe
- incoming fibers from lower retina stay inferior; form Meyer’s loop and travel in temporal lobe
- incoming fibers from upper retina stay superior; travel in parietal lobe
low retina
superior visual field
upper retina
inferior visual field
lesions in lower part of visual system (Meyer’s loop, temporal lobe white matter)
lead to upper visual field defects
lesions in the upper part of visual system (parietal lobe white matter)
lead to lower visual field defects
occipital lobe divided into…
- inferior visual field on top
- superior visual field on bottom
(divided by calcarine sulcus)
primary visual cortex lesions
- lesion in upper calcarine = lower field defect
- lesion in lower calcarine = upper field defect
testing visual fields
- perimetry: done with a computer; more precise, takes more time, more cost; looks for defects and charts their locations by having the patient stare at a light while other lights are flashed in the periphery
- confrontation method: done with fingers; less precise, quick and cheap
clinical signs of visual defects due to prechiasmal lesions
- if lesion is in retina –> visual field defects are usually: horizontal (left or right half of visual field), apex pints toward blind spot
- if lesion is in optic disc –> defecs are usually: vertical (superior or inferior half of visual field), constriction of visual field, enlarged blind spot
macular (central) vision sparing
- colateral from other arteries like middle cerebral artery
- spares the center of vision so that it is kept intact in both eyes
lesions in lateral side of occipital lobe beyond primary visual disturbances that are not associated with blindness
deficits in two streams of information: “what” and “where” pathways