The Functional Neuroanatomy of Temporal Discrimination

Abstract

Two identical stimuli, such as a pair of electrical shocks to the skin, are readily perceived as two separate events in time provided the interval between them is sufficiently long. However, as they are presented progressively closer together, there comes a point when the two separate stimuli are perceived as a single stimulus. Damage to posterior parietal cortex, peri-supplementary motor area (peri-SMA), and basal ganglia can disturb this form of temporal discrimination. Our aim was to establish, in healthy subjects, the brain areas that are involved in this process. During functional magnetic resonance imaging scanning, paired electrical pulses, separated by variable interstimulus intervals (5-110 msec), were delivered to different sites on one forearm (8 -64 mm from the midline). Subjects were required to simply detect the stimulus (control task) or to identify a stimulus property. For temporal discrimination (TD), subjects reported whether they felt one or two stimuli. For spatial discrimination, they reported whether the stimuli were located on the right or left side of the forearm. Subjects reported their choice by pressing a button with the opposite hand. Our results showed that discrimination, as opposed to simply detection, activated several brain areas. Most were common to both discrimination tasks. These included regions of prefrontal cortex, right postcentral gyrus and inferior parietal lobule, basal ganglia, and cerebellum. However, activation of pre-SMA and anterior cingulate was found to be specific to the TD task. This suggests that these two frontal regions may play a role in the temporal processing of somatosensory events.

Posteromedial Parietal Cortical Activity and Inputs Predict Tactile Spatial Acuity

“…Although this was not our primary interest in the present study, our finding of temporally specific activation for touch in the pre-SMA replicates that reported in a previous study (Pastor et al, 2004). In the present study, the pre-SMA activation extended posteriorly into the SMA; the division between these two regions corresponds to y ϭ 0, i.e., the coronal plane of the anterior commissure (Picard and Strick, 2001).…”

Neural Mechanisms for Binocular Depth, Rivalry and Multistability

“…Hence the results shed light on the functional role of frontoparietal activity and the mechanisms underlying perceptual reorganizations during bistable perception. This activation could reflect the change in sensory experience and task demand that occurs during transitions, which fits well with the known role of these areas in attention and decision making [65][66][67]70,78,79].…”

Dopamine Alters Tactile Perception in Parkinson's Disease

“…In healthy individuals, synchronized activation of minicolumns leads to perceptual binding such that the identity of the temporal order of stimuli is degraded 13 . In addition to SI, temporal discrimination is associated with neural responses in secondary somatosensory cortex, supplementary motor area, prefrontal cortex, inferior parietal lobule, basal ganglia, and the cerebellum 10,11,25,26 . It is unclear to what extent these loci and the spinal cord and thalamus may contribute to the synchronization effect.…”