Jd. Mendola et Br. Payne, DIRECTION SELECTIVITY AND PHYSIOLOGICAL COMPENSATION IN THE SUPERIOR COLLICULUS FOLLOWING REMOVAL OF AREAS 17 AND 18, Visual neuroscience, 10(6), 1993, pp. 1019-1026
Previous studies indicate that cortical areas 17 and 18 play a promine
nt role in generating the direction selectivities of neurons in the su
perior colliculus of the cat. This hypothesis was tested by quantifyin
g the activities of neurons in the superficial collicular layers in in
tact cats and cats which incurred ablation of areas 17 and 18 and part
of area 19. In addition, since behavioral and anatomical studies sugg
est a functional adjustment in the superior colliculus following remov
al of inputs from areas 17, 18, and 19 in the neonatal cat, we include
d a group of neonatally lesioned cats. Computation of an index of dire
ctionality indicated that the majority of neurons in intact cats prefe
rred movement in one direction, thus confirming reports of others. Fol
lowing ablation of areas 17 and 18 and part of area 19 in both groups
of lesioned cats, only modest changes in the population indices were d
etected when poorly responsive neurons were eliminated from the analys
es. Based upon levels of visually evoked neuronal activity, our data s
uggest a physiological compensation by neurons in stratum griseum supe
rficiale following removal of areas 17, 18, and 19 inputs. In the inta
ct and neonatally operated groups, activity in stratum griseum superfi
ciale is high, whereas in the adult lesioned group activity is low. In
stratum opticum, neuronal activity was similar in all three groups of
cats. These results show that neurons in stratum griseum superficiale
undergo a physiological compensation following removal of immature ar
eas 17 and 18.