ACTIVITY IN THE CAUDATE-NUCLEUS OF MONKEY DURING SPATIAL SEQUENCING

Citation
I. Kermadi et Jp. Joseph, ACTIVITY IN THE CAUDATE-NUCLEUS OF MONKEY DURING SPATIAL SEQUENCING, Journal of neurophysiology, 74(3), 1995, pp. 911-933
Citations number
43
Categorie Soggetti
Neurosciences,Physiology,Neurosciences,Physiology
Journal title
ISSN journal
00223077
Volume
74
Issue
3
Year of publication
1995
Pages
911 - 933
Database
ISI
SICI code
0022-3077(1995)74:3<911:AITCOM>2.0.ZU;2-4
Abstract
1. There are indications that the execution of behavioral sequences in volves the basal ganglia. In this study we examined the role of the ca udate nucleus in the construction, storage, and execution of spatial p lans. 2. Two monkeys (Macaca mulatta) were trained to perform sequence s of saccades and arm movements. The animals had to remember the order of illumination, variable from one sequence to another, of three fixe d spatial targets. After a delay, they had to visually orient toward, and press each target in the same order. Six different sequences were executed on the basis of the order of illumination of the targets. Sin gle cell activity was recorded from the four caudate nuclei of the two monkeys. 3. Neural activity was analyzed in each sequence during 10 d ifferent periods: the instruction period in which the targets were ill uminated, the three orientation periods toward the different targets, the three postsaccadic periods, and the three periods of target pressi ng. Statistical comparisons were made to detect differences between th e different sequences with respect to activity in each period (sequenc e specificity). 4. A total of 2,100 neurons were studied, of which 387 were task related. The task-related cells were found in both the head and the body of the caudate nucleus. 5. During central fixation, anti cipatory activity (n = 81) preceded onset of specific events. Four gro ups were considered: 1) neurons (n = 46) anticipating offset of the ce ntral fixation point, 2) neurons (n = 7) anticipating the illumination of any target, regardless of its spatial position or order of present ation (rank), 3) neurons (n = 17) anticipating the illumination of the first target, regardless of its spatial position, and 4) neurons (n = 11) anticipating the illumination of a given target, regardless of it s rank. 6. Phasic visual responses to target onset were observed in 48 cells. The cells responded primarily to the contralateral and upper t argets. In a majority (n = 35), visual responses were modulated by the rank of the target(s). Many cells (n = 20) responded only if the corr esponding target was first; other cells responded only if the target w as second or if it had complex time relationships with the other targe ts. 7. The responses of the cells to the same instruction stimuli repe ated twice in a row, and under the condition that the animal did not b ehaviorally use the first instruction in between, were tested. More th an one-third of the tested cells (n = 14) did not respond, or responde d very weakly, to the second instruction. 8. Visuomotor activity of in dividual caudate cells depended on the arm used to perform the target- pressing task. 9. Orientation-related activity (n = 110) was present w hen the animal made a saccade or a saccade and an arm movement toward a target. Many neurons (n = 48) were sequence specific. Their activity did not depend only on the spatial parameters of the current orientat ion, but also on the location and existence of the next target, i.e., on the characteristics of the spatial plan at the time of the orientat ion. 10. Postsaccadic activation was observed in 103 cells. In a major ity (n = 80), the activation occurred after saccades toward the upper and/or the ipsilateral target(s). Many neurons (n = 45) were sequence specific. Their activity appears as a cognitive phenomenon directly re lated to the selection of the successive targets. 11. Activity associa ted with the target pressing was observed in 77 cells. Thirty-eight (3 8) cells displayed a sequence specificity characterized by a preferenc e for the press at a given rank. The rank specificity is discussed in terms of anticipation and control of the visual feedbacks of the targe t presses. 12. A phasic activity (n = 21) followed an incorrect press. 13. Activity related to reward (n = 60) was a phasic discharge that o ccurred after the monkey's last target press and until the reward, and /or after the reward. 14. Taken together, the data are compatible with the hypothesis that the caudate nucleus participates in the construct ion, but not in the storage, of the spatial plans. Under control of th e spatial plans, the caudate nucleus would be instrumental in running the sequences. It would select the successive targets for the oculomot or apparatus as sequences progress. It would participate in the execut ion of the saccades and arm movements and would control the environmen tal changes that action generates.