Neuronal responses in macaque area PEc to saccades and eye position

• Published in: Neuroscience Vol. 156; no. 3; pp. 413 - 424
• Main Authors: Raffi, M, Ballabeni, A, Maioli, M.G, Squatrito, S
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.10.2008; Elsevier
• Subjects: Action Potentials - physiology; Animals; Behavior, Animal; Biological and medical sciences; Chi-Square Distribution; Eye and associated structures. Visual pathways and centers. Vision; eye movements; eye position; Fixation, Ocular - physiology; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; Macaca; Macaca fascicularis; Male; monkey; Neural Inhibition - physiology; Neurology; Neurons - physiology; Orientation - physiology; parietal cortex; Parietal Lobe - cytology; pause neurons; Reaction Time - physiology; Saccades - physiology; single unit recordings; Vertebrates: nervous system and sense organs; Visual Fields - physiology; Visual Perception - physiology; monkey; C; change in fixation point orientation; ERT; superior colliculus; inversion of fixation point movement; eye movements; parietal cortex; FP; Ku; lateral intraparietal area; pause neurons; second part of eye reaction time; antero-posterior; lever release; SC; supplementary eye field; FP INV; analysis of variance; ANOVA; beginning of the fixation point movement; single unit recordings; fixation point; static fixation; FEF; frontal eye field; eye reaction time; first part of eye reaction time; ERT1; ERT2; parieto-occipital sulcus; AP; eye position; LIP; FP MOV; lever pushing; FP FIX; POS; SEF; Kd; Central nervous system; Monkey; Eye movement; Encephalon; Eye; Visual system; Vertebrata; Mammalia; Neuron; Parietal cortex; Primates
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2008.08.018

Abstract Neurons in area PEc in the superior parietal cortex encode signals from different modalities, such as visual, extraretinal and somatosensory, probably combining them to encode spatial parameter of extrapersonal space to prepare body movements. This study reports the characterization of the functional properties of PEc non-visual neurons that showed saccade-related activity. We analyzed the pre- and post-saccadic firing activity in 189 neurons recorded in five hemispheres of three behaving monkeys. Spiking activity of PEc single neurons was recorded while the monkeys performed visually-guided saccades in a reaction time task. We found that 84% of neurons recorded from area PEc showed pre-saccadic activity with directional tuning. In 26% of neurons, we found inhibition of activity in the pre-saccadic period. The onset of this “pause” always started before the saccade and, in 51% of neurons, it was invariant among different gaze directions. The post-saccadic activity in these cells was either a phasic response with directional tuning (77%) and/or an eye position tuning (75%). The analysis of the preferred direction did not show hemispheric preference, however, for the majority of neurons, the angular difference in the preferred direction, in the pre- and post-saccadic period, was more than 60°. By confirming, therefore, that PEc neurons carry information about eye position, these novel findings open new horizons on PEc function that, to date, is not well documented. The pre-saccadic activity may reflect an involvement in saccade control, whereas post-saccadic activity may indicate a role in informing on the new eye position. These novel results about saccade and eye position processing may imply a role of area PEc in gaze direction mechanisms and, possibly, in remapping visual space after eye movements.