The critical events for motor-sensory temporal recalibration

Determining if we, or another agent, were responsible for a sensory event can require an accurate sense of timing. Our sense of appropriate timing relationships must, however, be malleable as there is a variable delay between the physical timing of an event and when sensory signals concerning that event are encoded in the brain. One dramatic demonstration of such malleability involves having people repeatedly press a button thereby causing a beep. If a delay is inserted between button presses and beeps, when it is subsequently taken away beeps can seem to precede the button presses that caused them. For this to occur it is important that people feel they were responsible for instigating the beeps. In terms of their timing, as yet it is not clear what combination of events is important for motor-sensory temporal recalibration. Here, by introducing ballistic reaches of short or longer extent before a button press, we varied the delay between the intention to act and the sensory consequence of that action. This manipulation failed to modulate recalibration magnitude. By contrast, introducing a similarly lengthened delay between button presses and consequent beeps eliminated recalibration. Thus it would seem that the critical timing relationship for motor-sensory temporal recalibration is between tactile signals relating to the completion of an action and the subsequent auditory percept

Optimal integration of auditory and vibrotactile information for judgments of temporal order

Recent research that assessed spatial judgments about multisensory stimuli suggests that humans integrate multisensory inputs in a statistically optimal manner by weighting each input by its normalized reciprocal variance. Is integration similarly optimal When humans judge the temporal properties of bimodal stimuli? Twenty-four participants performed temporal order judgments (TOJs,) about 2 spatially separated stimuli. Stimuli were auditory, vibrotactile, or both. The temporal profiles of vibrotactile stimuli were manipulated to produce 3 levels of precision for TOJs. In bimodal conditions, the asynchrony between the 2 unimodal stimuli that comprised it bimodal Stimulus was manipulated to determine the weight given to touch. Bimodal performance on 2 measures-judgment uncertainty and tactile weight-was predicted With unimodal data. A model relying exclusively on audition wits rejected on the basis of both measures. A second model that selected the best input on each trial did not predict the reduced judgment uncertainty observed in bimodal trials. Only the optimal Maximum-likelihood-estimation model predicted both judgment uncertainties and weights the model's validity is extended to TOJs. Alternatives for modeling the process of event sequencing based on integrated multisensory inputs are discussed

Vibrotactile-auditory interactions are post-perceptual

Vibrotactile stimuli can elicit compelling auditory sensations, even when sound energy levels are minimal and undetectable. It has previously been shown that subjects judge auditory tones embedded in white noise to be louder when they are accompanied by a vibrotactile stimulus of the same frequency. A first experiment replicated this result at four different levels of auditory stimulation (no tone, tone at detection threshold, tone at 5 dB above threshold, and tone at 10 dB above threshold). The presence of a vibrotactile stimulus induced an increase in the perceived loudness of auditory tones at three of the four values in this range. In two further experiments, a 2-interval forced-choice procedure was used to assess the nature of this cross-modal interaction. Subjects were biased when vibrotaction was applied in one interval, but applying vibrotaction in both intervals produced performance comparable to conditions without vibrotactile stimuli. This demonstrates that vibrotaction is sometimes ignored when judging the presence of an auditory tone. Hence the interaction between vibrotaction and audition does not appear to occur at an early perceptual level

Neural correlates of subjective timing precision and confidence

Humans perceptual judgments are imprecise, as repeated exposures to the same physical stimulation (e.g. audio-visual inputs separated by a constant temporal offset) can result in different decisions. Moreover, there can be marked individual differences – precise judges will repeatedly make the same decision about a given input, whereas imprecise judges will make different decisions. The causes are unclear. We examined this using audio-visual (AV) timing and confidence judgments, in conjunction with electroencephalography (EEG) and multivariate pattern classification analyses. One plausible cause of differences in timing precision is that it scales with variance in the dynamics of evoked brain activity. Another possibility is that equally reliable patterns of brain activity are evoked, but there are systematic differences that scale with precision. Trial-by-trial decoding of input timings from brain activity suggested precision differences may not result from variable dynamics. Instead, precision was associated with evoked responses that were exaggerated (more different from baseline) ~300 ms after initial physical stimulations. We suggest excitatory and inhibitory interactions within a winner-take-all neural code for AV timing might exaggerate responses, such that evoked response magnitudes post-stimulation scale with encoding success

Spatial grouping resolves ambiguity to drive temporal recalibration.

Cross-modal temporal recalibration describes a shift in the point of subjective simultaneity (PSS) between 2 events following repeated exposure to asynchronous cross-modal inputs-the adaptors. Previous research suggested that audiovisual recalibration is insensitive to the spatial relationship between the adaptors. Here we show that audiovisual recalibration can be driven by cross-modal spatial grouping. Twelve participants adapted to alternating trains of lights and tones. Spatial position was manipulated, with alternating sequences of a light then a tone, or a tone then a light, presented on either side of fixation (e.g., left tone-left light-right tone-right light, etc.). As the events were evenly spaced in time, in the absence of spatial-based grouping it would be unclear if tones were leading or lagging lights. However, any grouping of spatially colocalized cross-modal events would result in an unambiguous sense of temporal order. We found that adapting to these stimuli caused the PSS between subsequent lights and tones to shift toward the temporal relationship implied by spatial-based grouping. These data therefore show that temporal recalibration is facilitated by spatial grouping. (PsycINFO Database Record (c) 2011 APA, all rights reserved)

Increased motor cortex excitability for concealed visual information

Deceptive behaviour involves complex neural processes involving the primary motor cortex. The dynamics of this motor cortex excitability prior to lying are still not well understood. We sought to examine whether corticospinal excitability can be used to suggest the presence of deliberately concealed information in a modified version of the Guilty Knowledge Test (GKT). Participants pressed keys to either truthfully or deceitfully indicate their familiarity with a series of faces. Motor-evoked-potentials (MEPs) were recorded during response preparation to measure muscle-specific neural excitability. We hypothesised that MEPs would increase during the deceptive condition not only in the lie-telling finger but also in the suppressed truth-telling finger. We report a group-level increase in overall corticospinal excitability 300 ms following stimulus onset during the deceptive condition, without specific activation of the neural representation of the truth-telling finger. We discuss cognitive processes, particularly response conflict and/or automated responses to familiar stimuli, which may drive the observed non-specific increase of motor excitability in deception

Inside the brain of an elite athlete: The neural processes that support high achievement in sports

Events like the World Championships in athletics and the Olympic Games raise the public profile of competitive sports. They may also leave us wondering what sets the competitors in these events apart from those of us who simply watch. Here we attempt to link neural and cognitive processes that have been found to be important for elite performance with computational and physiological theories inspired by much simpler laboratory tasks. In this way we hope to inspire neuroscientists to consider how their basic research might help to explain sporting skill at the highest levels of performance

Teaching Wildlife Damage Management Through Service-Learning

As human-wildlife conflicts in South Carolina continue to increase, it became evident that students in the natural resource majors at Clemson University were not receiving the proper training and exposure to wildlife damage issues and management. To address this need, an undergraduate and graduate course was developed to expose students to various techniques used to reduce human-wildlife conflicts. Other topic areas included the philosophical, sociological, ecological and economic basis for controlling damage caused by individual animals or populations of problem wildlife. The course involves a high degree of service-learning addressing human-wildlife conflict issues in South Carolina

Force platform recordings in the diagnosis of primary orthostatic tremor

Primary orthostatic tremor (OT) consists of rhythmical muscle contractions at a frequency of around 16 Hz, causing discomfort and/or unsteadiness while standing. Diagnosis has hitherto relied on recording Electromyography (EMG) from affected muscles. The main aim of this study was to see if the characteristic postural tremor in OT can be identified with force platforms. We also quantified postural sway in OT patients to assess their degree of objective unsteadiness. Finally, we investigated the time relations between bursts of activity in the various affected muscle groups. Subjects stood on a force platform with concurrent multichannel surface EMG recordings from the lower limbs. Seven patients with clinical and EMG diagnosis of OT were examined and the force platform data compared with those of 21 other neurological patients with postural tremor and eight normal controls. All OT patients had high frequency peaks in power spectra of posturography and EMG recordings (12–16 Hz). No such high frequency activity was evident in patients with Parkinson's disease, cerebellar degenerations, essential tremor or in healthy controls. Additionally, OT patients showed increased sway at low frequencies relative to normal controls, suggesting that the unsteadiness reported by OT patients is at least partly due to increased postural sway. Examination of EMG timing showed fixed patterns of muscle activation when maintaining a quiet stance within but not across OT patients. These data show a high correlation between EMG and posturography and confirm that OT may be diagnosed using short epochs of force platform recordings