Cerebral Cortex, Vol 7, 317-326, Copyright © 1997 by Oxford University Press
R Romo, H Merchant, A Zainos and A Hernandez
In this paper we describe a type of neuron of the medial premotor cortex
(MPC) that discharged differentially during a categorization task and
reflected in their activity whether the speed of a tactile stimulus was low
or high. The activity of these neurons was recorded in the MPC
contralateral (right MPC, n = 88) and ipsilateral (left MPC, n = 103) to
the stimulated hand of four monkeys performing this somesthetic task.
Animals performed the task by pressing with the right hand one of two
target switches to indicate whether the speed of probe movement across the
skin of the left hand was low or high. Differential responses of MPC
neurons occurred during the stimulus and reaction time period. We used an
analysis based on signal detection theory to determine whether these
differential responses were associated with the animal's decision.
According to this analysis, 104 of the 191 neurons (right MPC, n = 48; left
MPC, n = 56) coded the categorization of the stimulus speeds (categorical
neurons). In a light instruction task, we tested the possibility that the
categorical neurons (n = 71) were associated with the intention to press,
or with the trajectory of the hand to one of the two target switches used
to indicate categorization. In this situation, each trial began as in the
somesthetic categorization task, but one of the two target switches was
illuminated beginning with the skin indentation, continued during the delay
period and turned off when the probe was lifted off from the skin. This
condition instructed the animal which target switch was required to be
pressed for reward. Very few neurons (14 of 71) maintained their
differential responses observed in the categorization task. Some
categorical neurons (n = 5) were also studied; the animal categorized the
tactile stimulus speeds, but knew in advance whether the stimulus speed was
low or high (categorization + light instruction). This was made by
illuminating one of the two target switches which was associated with the
stimulus speed. The categorical response was considerably attenuated in
this condition. Interestingly, during the delay period, these neurons
reflected in their activity whether the stimulus was low or high. A number
of the categorical MPC neurons (n = 30) were studied when the same set of
stimuli, used in the categorization, were delivered passively. None of
these neurons responded in this condition. These results suggest that the
MPC, apart from its well-known role in motor behavior, is also involved in
the animal's decision during the execution of this learned somesthetic
task.
ARTICLES
Categorical perception of somesthetic stimuli: psychophysical measurements correlated with neuronal events in primate medial premotor cortex
Instituto de Fisiologia Celular, Universidad Nacional Autonoma de Mexico, Mexico DF, Mexico.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  L. Lemus, A. Hernandez, R. Luna, A. Zainos, V. Nacher, and R. Romo Neural correlates of a postponed decision report PNAS, October 23, 2007; 104(43): 17174 - 17179. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. R. Pruett Jr., R. J. Sinclair, and H. Burton Neural Correlates for Roughness Choice in Monkey Second Somatosensory Cortex (SII) J Neurophysiol, October 1, 2001; 86(4): 2069 - 2080. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Shima and J. Tanji Both Supplementary and Presupplementary Motor Areas Are Crucial for the Temporal Organization of Multiple Movements J Neurophysiol, December 1, 1998; 80(6): 3247 - 3260. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Salinas and R. Romo Conversion of Sensory Signals into Motor Commands in Primary Motor Cortex J. Neurosci., January 1, 1998; 18(1): 499 - 511. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Hernandez, E. Salinas, R. Garcia, and R. Romo Discrimination in the Sense of Flutter: New Psychophysical Measurements in Monkeys J. Neurosci., August 15, 1997; 17(16): 6391 - 6400. [Abstract] [Full Text] [PDF]
|
|