CODING OF PERIPERSONAL SPACE IN INFERIOR PREMOTOR CORTEX (AREA F4).
Fogassi, L., V. Gallese, L. Fadiga, G. Luppino, M. Matelli and G. Rizzolatti.
Istituto di Fisiologia Umana, Universit[circumflex]e di Parma, I-43100
APStracts 3:0016N, 1996.
SUMMARY AND CONCLUSIONS
1. We studied the functional properties of neurons in the caudal part of
inferior area 6 (area F4) in awake monkeys. In agreement with previous
reports, we found that the large majority (87%) of neurons responded to
sensory stimuli. The responsive neurons fell into three categories:
somatosensory neurons (30%), visual neurons (14%), and bimodal, visual and
somatosensory, neurons (56%). Both somatosensory and bimodal neurons typically
responded to light touch of the skin. Their RFs were located on the face,
neck, trunk, and arms. Approaching objects were the most effective visual
stimuli. Visual RFs were mostly located in the space near the monkey
(peripersonal space). Typically they extended in the space adjacent to the
tactile RFs. 2. The coordinate system in which visual RFs were coded was
studied in 110 neurons. In 94 neurons the RF location was independent of eye
position remaining in the same position in the peripersonal space regardless
of eye deviation. The RF location with respect to the monkey was not modified
by changing monkey position in the recording room. In 10 neurons the RFs
location followed the eye movements, remaining in the same retinal position
(retinocentric RFs). For the remaining 6 neurons the RF organization was not
clear. We will refer to F4 neurons with RF independent of eye position as
somatocentered neurons. 3. In most somatocentered neurons (43 out of 60
neurons) the background level of activity and the response to visual stimuli
were not modified by changes in eye position, while they were modulated in the
remaining 17. It is important to note that eye deviations were constantly
accompanied by a synergic increase of the activity of the ipsilateral neck
muscles. It is not clear, therefore, whether the modulation of neuron
discharge depended on eye position or was a consequence of changes in neck
muscle activity. 4. The effect of stimulus velocity (20 to 80 cm/s) on neuron
response intensity and RF extent in depth was studied in 34 somatocentered
neurons. The results showed that in most neurons the increase of stimulus
velocity produced an expansion in depth of the RF. 5. We conclude that space
is coded differently in areas that control somatic and eye movements. We
suggest that space coding in different cortical areas depends on the
computational necessity of the effectors they control.
Received 13 February 1995; accepted in final form 11 December 1995.
APS Manuscript Number J97-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96