Reading - Kolb & Whishaw � Fundamentals of Neuropsychology 4th ed

the temporal lobe (incl the auditory regions of the superior temporal gyrus), the visual regions of TE, and the superior temporal sulcus, and amygdala

there are also connections from:

the somatosensory cortex (area 43), gustatory cortex (in the insula), and olfactory regions of the pyriform cortex

the gustatory + olfactory connections are localised in the orbital cortex

the visual, auditory + somatosensory connections go largely to area 12

projects subcortically to the amygdala and hypothalamus

this provides a route for influencing the autonomic system (important in emotional responses)

receive a significant input from dopaminergic cells in the tegmentum

(plays an important role in regulating how prefrontal neurons react to stimuli, incl stressful ones) � abnormalities in this projection play a central role in schizophrenia

A theory of frontal lobe function

example of: shopping for various ingredients to cook a meal for friends after work in a hurry

frontal lobe injury cannot manage this. fundamental requirements are:

plan behaviour in advance, selecting from many options

time constraint, so ignore stimuli and persists in the taks at hand

keep track of where we have been and done

general function of the frontal lobe:

behavioural requirements = temporal organisation of behaviour

motor cortex: responsible for making movements

premotor cortex: selects movements

Functions of the prefrontal cortex

prefrontal cortex: controls the cognitive processes so that appropriate movements are selected at the correct time + place

this selection may be controlled by internalised information, or may be made in response to context

the internalised record of what has just occurred is independent of the existing sensory information = the STM

temporal memory = neural record of recent events

events = either things or places

thus information is derived from the object-recognition or spatial streams of sensory processing

(both project to the prefrontal cortex, though to different parts)

i.e. spatial + object information are stored in temporal memory � but localised in different places in the frontal cortex

dorsolateral areas = especially involved in the selection of behaviour based on temporal memory (if defective, become dependent on environmental cues)

so frontal lobe injury �/span> difficulty inhibiting behaviour directed to external stimuli, as opposed to being controlled by internalised knowledge

behaviour = context-dependent

Goodall: the current make-up of the social group dictates the behaviour of each chimpanzee (e.g. bold + relaxed vs quiet + nervous with a different group of animals)

can be serious consequences in wrongly evaluating context

primates: highly social, hence the need for large frontal lobe

choice of behaviour in context requires detailed sensory information:

conveyed to the inferior frontal cortex from the temporal lobe

amygdala supplies the affective context

inferior frontal lesoins �/span> difficulty with context, especially in social situations

Asymmetry of frontal lobe function

functional asymmetry in parietal + temporal association cortex � similar in frontal lobes

left: preferential role in language-related movements, incl speech

right: greater role in other movements, e.g. facial expression

however, both frontal lobes play roles in nearly all behavoiur

laterality of function = relative, not absolute

Symptoms of frontal lobe lesions

Summary of major symptoms of frontal lobe damage

*Most probable symptom*	*Lesion site*	*Basic reference*
Disturbances of motor function
loss of fine movements loss of strength poor movement programming poor voluntary eye gaze poor corollary discharge Broca�s aphasia	area 4 areas 4, 6; dorsolateral premotor dorsolateral frontal eye fields dorsolateral, premotor area 44	Kyupers, 1981 Leonard et al., 1988 Roland et al., 1980 Kolb & Milner, 1981 Guitton et al., 1982 Teuber, 1964 Brown, 1972
Loss of divergent thinking
reduced spontaneity poor strategy formation	orbital dorsolateral?	Jones-Gotman and Milner, 1977 Shallice & Evans, 1978
Environmental control of behaviour
poor response inhibition risk-taking and rule-breaking impaired associative learning	prefrontal prefrontal dorsolateral	Milner, 1964 Milner, 1985 Petrides, 1982
Poor temporal memory
poor recency memory poor frequency estimate poor self-order recall poor delayed response	dorsolateral dorsolateral dorsolateral dorsolateral	Milner, 1974 Smith & Milner, 1985 Petrides and Milner, 1982 Freedman & Oscar-Berman, 1986
Impaired social behaviour	orbital; dorsolateral	Blumer & Benson, 1975
Altered sexual behaviour	orbital	Walker & Blumer, 1975
Impaired olfactory discrimination	orbital	Potter & Butters, 1980
Disorders associated with damage to the face area	face	Taylor, 1979

Summary

frontal lobe � endpoint for the spatial and object-recognition functions initiated in the occiptal lobe

the frontal lobe�s function = to select behaviours with respect to context and internalised knowledge

3 distinct functional zones:

motor cortex � responsible for making movements

premotor cortex � selects movements

lateral � selects behaviours in response to environmental cues

supplementary � selects behvaiorus on the basis of internalised knowledge

prefrontal cortex � controls the cognitive processes so that appropriate movements are selected at the right time and place

dorsolateral zone � selects behvaoiur with respect to temporal memory

inferior � selects behaviour with respect to context (current + based on knowledge)

Chapter 19 � Spatial behaviour � The frontal cortex

frontal cortex = important for spatial discriminations

Nakamura � monkeys: spared all the visual areas of the posterior cortex, but removed all the cortex anterior to it

the monkeys failed to show any signs of vision, but recordings of single cell activity in the visual areas showed the cells to be functioning normally

i.e. removal of the frontal cortex �/span> chronically blind, even though the visual system is functioning

restricted lesions in the visual cortex �/span> more selective impairments:

Haaxma & Kuypers: if the finger area of the motor cortex is disconnected from the visual centers

then a monkey cannot use the pincer grasp to pick up food

difficult to distinguish: impairments object detection from impairments of memory

Goldman-Rakic: rhesus monkeys, lesions in the frontal cortex along the principal sulcus

the monkeys were trained to direct their gaze and fixate on a spot of light flashed in their visual field, once the spot had disappeared

unilateral lesions: could only direct their gaze to direct when no delay, not even with short delays

selective deficits in different parts of the visual field (by varying the location of the lesion)

demonstrates that:

the principal sulcus contains a mechanism for guiding responses on the basis of stored information, when there are no external cues

the memory for the location of objects may be mapped in visuospatial coordinates

parallel set of experiments: monkeys have to reach to a target

lesions to the principal sulcus:

delayed-response taks: location of the object is the relevant task variable

�/span> impairments after short delays

but other discrimination tasks that don�t require memory are not impaired

Passingham rhesus monkeys with principal sulcus lesions:

monkeys trained to retrieve peanuts from behind 25 different doors in the shortest number of trials, without returning to a door twice

tested spatial memory for doors it had opened

monkeys with lesions: severely impaired

Petrides & Milner: patients presented with a set of pages containing the same array of visual stimuli, but varied positions on the page

point to one of the stimuli on each page, but not to the same place twice

needed to remember the selections they had made previously

frontal lobe damage �/span> impairments

Connections

frontal cortex has important connections with the basal ganglia

perhaps expected: basal ganglia lesions �/span> similar spatial memory impairments

Ingle & Hoff: frogs impaired in this way

visible barrier placed beside frog, then removed,

delay, then large dark object looms towards frog, which leaps away

normal frogs avoided leaping into or around the barrier�s previous location

frogs with basal ganglia lesions: behaved as if they failed to remember where the barrier had been, though they avoided it when it was present