Greg Detre
Wednesday, 17 May, 2000
Rolls � B&B III
Andersen,R.A. (1995) Coordinate transformations and motor planning in the posterior parietal cortex. Ch. 33, pp. 519-532 in The Cognitive Neurosciences, ed. M.S.Gazzaniga. Cambridge, Mass.: MIT Press. [BHa:G025 oversize]
*Kolb, B. & Whishaw, I.Q. (1996) Fundamentals of Human Neuropsychology. 4th edn. New York: W.H. Freeman. Section on Parietal Disorders: pp. 271-284. [BHa.K 083]
damage to parietal lobe �/span> diverse physical symptoms, especially non-verbal cognitive functions
= for spatial functions + �where� system
principle thalamocortical projections to the parietal cortex:
from the LP-pulvinar complex (receives from the superior colliculus and the pretectum)
also the thalamic intra-laminar nuclei
horse-radish peroxidase and radioactive amino acids
connections from the parietal cortex = hierarchically organised and gather at common destinations (e.g. prefrontal cortex, limbic system and the depth of STS)
integrating somatosensory and visual input (and other sensory input) � mainly for control of movement
dated idea: map of the location of objects around the body, common to all senses (since movement with different senses is common/easy)
no evidence for single unified spatial map
different representations of space for different:
behavioural needs
levels of complexity (simple movements / topographical knowledge)
viewer-centred system � the system that identifies the location, local orientation and motion of an object relative to the viewer
many visual areas in the posterior parietal region
and also multiple projections to motor systems for eyes + limbs
connections to prefrontal: has a role in the STM of location of events in space
monkey neurons: activity dependent on concurrent behaviour of the animal with respect to visual stimulation
response of posterior parietal neurons during sensory input and during movement
all respond to movements of the eyes and to the position of the eye in its socket (some are most responsive to behaviourally relevant stimulus, e.g. reward)
some are barely activated by stationary visual stimuli but respond strongly when attention is directed or eye/arm movement made towards stimulus
some respond to manipulation of the object, or its structural features
Stein (1992) � 2 characteristics of all posterior parietal neurons:
1. combinations of sensory, motivational and motor information are received
2. response is greatest when the animal attends to, or moves towards, a target
we might then expect posterior parietal neurons to be transforming sensory information into commands for directing attention and guiding motor outputs
human posterior parietal lesions:
impaired in distinguishing left from right
impaired mental manipulations of objects
spatial deficits � perhaps due to damage to temporal-parietal polysensory regions(Goodale & Milner, 1993), rather than to the dorsal stream�s role in visuomotor guidance
right hemisphere lesions (greater polysensory growth in the right hemisphere) �/span> greater deficits on complex spatial tasks
co-ordinate transformation for determining spatial location and forming plans
Andersen - combine information from different modalities to form 3 types of abstract representation:
head-centred � combines information about eye position + the location of a visual stimulus on the retina
body-centred � combines information about head, eye and retinal position
world-centred � combines vestibular signals with eye poistion and retinal position
what is the �hierarchical organisation of the parietal cortex connections�?
depth of STS
ERPs
anderson�s planar gain fields
head/body/world-centred � other �centred views elsewhere?
LIP neurons
neuron vs neurone?
gain fields
cartesian co-ordinate system of world with >=� 3 neurons
unilateral lesion = damage to one side only?
apraxia = inability to perform given purposive actions;
disturbance of movement where there is damage to skilled movement that is not
caused by weakness, an inability to move, abnormal tone or posture,
intellectual deterioration or other disorders of movement such as tremor
ataxia = lack of coordination of movement, esp. as
causing unsteadiness of gait
anasagnosia = lack of bodily signals? not realising there�s anything
wrong?
neglect = ignoring stimuli?
lobule = a small lobe; a lobular subdivision of a lobe.
lobe = a roundish projecting part, usually one of two or more similar
portions into which an object is divided by a fissure; esp. one of the
divisions of the liver, lungs, brain, or other organ
cingulate cortex
paraphasias
acalculia = an inability to do arithmetic
ideomotor apraxia = movements are not able to be copied by the patient,
or the patient cannot make gestures
construction apraxia = where patients are unable to perform activities
such as assembling, building or drawing
somato/agnosia