A workstation interface for measuring interspike intervals

Attentional modulation of receptive field structure in area 7a of the behaving monkey

Spatial attention modulates the activity of inferior parietal neurons. A statistically rigorous approach to classical retinotopic mapping was used to quantify the receptive fields of area 7a neurons under 2 attentional conditions. Measurements were made with retinal stimulation held constant and the locus of attention manipulated covertly. Both tasks required central fixation but differed in the locus of covert attention (either on the center fixation point or on a peripheral square target in one of 25 locations). The neuron's identity over the recording session was confirmed using chaos theory to characterize unique temporal patterns. Sixty-six percent of the neurons changed prestimulus activity based on task state. Retinotopic mapping showed no evidence for foveal sparing. Attentional factors influenced visual responses for approximately 30% of the neurons. Two types of modulation were equally observed. One group of cells had a multiplicative scaling of response, with equal instances of enhancement and suppression. A second group of cells had a complex interaction of visual and attentional signals, such that spatial tuning was subject to a nonlinear modulation across the visual field based on attentional constraints. These 2 cell groups may have different roles in the shift of attention preceding motor behaviors and may underlie shifts in parietal retinotopic maps observed with intrinsic optical imaging.

Three-dimensional structure-from-motion selectivity in the anterior superior temporal polysensory area, STPa, of the behaving monkey

Human and non-human primates are able to perceive three-dimensional structure from motion displays. Three-dimensional structure-from-motion (object-motion) displays were used to test the hypothesis that neurons in the anterior division of the superior temporal polysensory area (STPa) of monkeys can selectively respond to three-dimensional structure-from-motion. Monkeys performed a reaction time task that required the detection of a change in the fraction of structure in three-dimensional transparent sphere displays. Neurons were able to distinguish structured and unstructured three-dimensional optic flow. These cells could differentiate the change in structure-from-motion at stimulus presentation and when the animal was detecting the amount of structure in the display. Some of these neurons were also tuned for characteristics of the sphere stimuli. Cells were also tested with navigational motion and many were found to respond both to three-dimensional structure-from-motion and navigational motion. These results suggest that STPa neurons represent specific aspects of three-dimensional surface structure and that neurons within STPa contribute to the perception of three-dimensional structure-from-motion.

A microcomputer program for automated neuronal spike detection and analysis

A system for on-line spike detection and analysis based on an IBM PC/AT compatible computer, written in TURBO PASCAL 6.0 and using commercially available analog-to-digital hardware is described here. Spikes are detected by an adaptive threshold which varies as a function of signal mean and its variability. Since the threshold value is determined automatically by the signal-to-noise ratio analysis, the user is not actively involved in controlling its level. This program has been reliably used for the detection and analysis of the spike discharge of vestibular system afferent neurons. It generates the interval-joint distribution graph, the interval histogram, the autocorrelation function, the autocorrelation histogram, and phase-space graphs, thus, providing a complete set of graphical and statistical data for the characterization of the dynamics of neuronal spike activity. Data can be exported to other software such as Excel, Sigmaplot and MatLab, for example.

A general-purpose system for long-term recording from a microelectrode array coupled to excitable cells

A PC-based system for acquisition and processing of data from excitable cells on a microelectrode array is described. Simple and low-cost amplification and filtering custom stages are used. A software package for processing acquired data is proposed.