i would be grateful to anyone who can answer this, because i'm doing my
third year project on the relationship between visual mental imagery and
spatial learning/recall, and am trying to get clear as much as we do know
about these things before i start my experiment.
i'm reading
1) Marc Jeannerod's paper on THE REPRESENTING BRAIN: NEURAL CORRELATES OF
MOTOR INTENTION AND IMAGERY
http://www.cogsci.soton.ac.uk/bbs/Archive/bbs.jeannerod.html
2) Vittorio Gallese's paper on The acting brain: reviewing the
neuroscientific evidence- A brief review of The Paradox of
Self-Consciousness.
http://www.uniroma3.it/kant/field/bermudezsymp_gallese.htm
it sounds to me like they're describing the same thing but from different
angles (marc's interested in imagery, vittorio representation) in the bits
i've summarised below. it also reminds me of the ventral v/s dorsal stream
for object processing (what v/s where) i've come across before.
so my question is, is
brodmann area 6 = The posterior parietal cortexes, and area F4 in the
ventral premotor cortex = dorsal stream?
brodmann area 7 = F5 and the AIP parietal area = ventral stream?
according to marc: Elementary schemas are behaviours due to activation of
areas 6 and 7. These areas are activated by subgoals. Single cell recordings
in monkeys show that, in visually guided movements, the majority of neurons
in the premotor cortex are preferentially active in relation to motor
preparation, rather than to spatial attention or memory (Boussaoud et al.,
1996 ). Area 6 neurons prepare distal movements and relate to the way the
hand is shaped prior to and during the action directed toward a target
object. It is necessary for deciding which of two actions to choose on a
particular object (e.g. to pull or rotate a lever). Area 7 neurons are
activated during manipulation of visual objects of a given configuration
(e.g. a push-button, a handle). They are not activated by either perception
of the object alone or movements towards the object in the dark.
according to vittorio: We have multiple neural representations of given
types of actions and objects. Specialised neural circuits' representational
rules vary along 2 dimensions: self-referent v/s object-centred, and degree
of specificity v/s generalisation. The posterior parietal cortexes, and area
F4 in the ventral premotor cortex, code the localisation of objects in that
space whose outer limits are defined by the working space of the body
effectors (Gentilucci et al. 1988 ; Graziano et al., 1994 ; Fogassi et al.,
1996 ; Rizzolatti et al., 1997 ; Graziano and Gross, 1998 ; Duhamel et al.,
1998 ). This spatial coding uses a frame of reference relative to ourselves,
often to our body parts. The spatial coding of these brain areas is the
location with respect to our own body of whatever will become the target of
a purposeful action. The characteristics of that object are far less
important, and these areas may not even detect shape, colour, size.
F5 is the most rostral area of the ventral premotor cortex of the macaque
brain. It has two components: 1) Buried within the posterior bank of the
inferior arcuate sulcus is the rostral part made up of neurons activated by
goal-directed hand and mouth actions or triggered by visual properties of
objects cuing this motor action. 2) The caudal bulge on F5 contains "mirror"
(imitative) neurons, which share the same motor actions as the rostral
neurons, but are triggered by the appropriate hand or mouth movements of
others, not the object. In the rostral sector of the premotor area F5 and
the AIP parietal area, these neurons detect the physical characteristics of
the object more than the spatial location. The reference frame is
object-centred in that spatial location with regards to self is unimportant,
but nevertheless the relationship of the object to the person in terms of
generating motor activity is critical. The object is represented as an
intentional, relational motor schema.
--
Shamim Khaliq shamimkhaliq at hotTAKETHISOFFmail.com
<http://shamimkhaliq.50megs.com/>
