Sarah C. Tyler

Feature-based attention promotes biological motion recognition

Motion perception is important for visually segregating and identifying objects from their surroundings, but in some cases extracting motion cues can be taxing to the human attention system. We measured the strength of feature salience required for individuals to correctly judge three types of moving events: biological motion, coherent motion, and multiple object tracking. The motion animations were embedded within a larger Gabor grid and constructed such that motion was conveyed by a salient single-feature dimension (second order) or by alternating across equisalient feature dimensions (third order). In the single-feature displays, we found biological motion to require less difference in the Gabor features (relative to background) to yield equivalent task performance as the coherent motion or multiple object tracking. This main effect of feature magnitude may reflect the inherent salience of biological motion as a visual stimulus. In the alternating-feature displays, both the biological motion and coherent motion discriminations needed additional salience, as compared to the single-feature displays, to achieve threshold discrimination levels. Accuracy in the multiple object tracking task did not vary as a function of salience. Together, these findings demonstrate the effectiveness with which attention-based motion mechanisms operate in complex dynamic sequences and argue for a critical role of feature-based attention in promoting biological motion perception.

Review: network connectivity of the right sts in three social perception localizers

The posterior STS (pSTS) is an important brain region for perceptual analysis of social cognitive cues. This study seeks to characterize the pattern of network connectivity emerging from the pSTS in three core social perception localizers: biological motion perception, gaze recognition, and the interpretation of moving geometric shapes as animate. We identified brain regions associated with all three of these localizers and computed the functional connectivity pattern between them and the pSTS using a partial correlations metric that characterizes network connectivity. We find a core pattern of cortical connectivity that supports the hypothesis that the pSTS serves as a hub of the social brain network. The right pSTS was the most highly connected of the brain regions measured, with many long-range connections to pFC. Unlike other highly connected regions, connectivity to the pSTS was distinctly lateralized. We conclude that the functional importance of right pSTS is revealed when considering its role in the large-scale network of brain regions involved in various aspects of social cognition.

The Pivotal Role of the Right Parietal Lobe in Temporal Attention.

The visual system is extremely efficient at detecting events across time even at very fast presentation rates; however, discriminating the identity of those events is much slower and requires attention over time, a mechanism with a much coarser resolution [Cavanagh, P., Battelli, L., & Holcombe, A. O. Dynamic attention. In A. C. Nobre & S. Kastner (Eds.), The Oxford handbook of attention (pp. 652–675). Oxford: Oxford University Press, 2013]. Patients affected by right parietal lesion, including the TPJ, are severely impaired in discriminating events across time in both visual fields [Battelli, L., Cavanagh, P., & Thornton, I. M. Perception of biological motion in parietal patients. Neuropsychologia, 41, 1808–1816, 2003]. One way to test this ability is to use a simultaneity judgment task, whereby participants are asked to indicate whether two events occurred simultaneously or not. We psychophysically varied the frequency rate of four flickering disks, and on most of the trials, one disk (either in the left or right visual field) was flickering out-of-phase relative to the others. We asked participants to report whether two left-or-right-presented disks were simultaneous or not. We tested a total of 23 right and left parietal lesion patients in Experiment 1, and only right parietal patients showed impairment in both visual fields while their low-level visual functions were normal. Importantly, to causally link the right TPJ to the relative timing processing, we ran a TMS experiment on healthy participants. Participants underwent three stimulation sessions and performed the same simultaneity judgment task before and after 20 min of low-frequency inhibitory TMS over right TPJ, left TPJ, or early visual area as a control. rTMS over the right TPJ caused a bilateral impairment in the simultaneity judgment task, whereas rTMS over left TPJ or over early visual area did not affect performance. Altogether, our results directly link the right TPJ to the processing of relative time.

Rapid effect of high-frequency tRNS over the parietal lobe during a temporal perceptual learning task

INTRODUCTION Transcranial random noise stimulation (tRNS) is a noninvasive neurostimulation technique in which random current levels applied to scalp electrodes elicit temporary changes in cortical excitability (Terney et al., 2008). This experiment explores modulatory effects of high-frequency tRNS on neural plasticity during a temporal perceptual learning task. We measured sensitivity to onset asynchronies (SOAs) during a temporal order judgment task as a function of both practice and active stimulation. METHODS Twenty-four subjects were randomly assigned to one of four conditions: hf-tRNS (up to 1000 Hz) over hMT+; hf-tRNS over parietal cortex; sham stimulation; and behavior only. Subjects undergoing active hf-tRNS were stimulated for 20 consecutive minutes concurrent with the task. Subjects viewed two discs flickering black and white for 1000 ms at 7.5 Hz. These discs were presented with onset asynchronies ranging from -66 ms (left disc first) to +66 ms (right disc first). During the flicker cycle, each disc was temporarily displayed as a Gabor for 133 ms (sp. frequency: 1.25 cycle/deg). Subjects judged whether the right or left disc appeared as a Gabor first. Feedback was provided for five out of six blocks. RESULTS SOA values across blocks were compared to determine sensitivity to the timing of Gabor onsets. As the experiment progressed, subjects exposed to parietal hf-tRNS were significantly better at correctly judging temporal order of the embedded Gabor discs at small onset asynchronies (F(3,20)=14.37; p = 0) as compared to all other conditions. CONCLUSIONS Our results show the quick effect that parietal tRNS has in improving perceptual sensitivity during tasks that require attention to temporal patterns. These results shows promising insight into the relationship between cortical stimulation and neural plasticity, leading the way to neurostimulation as a possible therapy for patients suffering from neurological attention disorders. Meeting abstract presented at VSS 2015.

Rapid Improvement on a Temporal Attention Task within a Single Session of High-frequency Transcranial Random Noise Stimulation

This study explored the modulatory effects of high-frequency transcranial random noise stimulation (tRNS) on visual sensitivity during a temporal attention task. We measured sensitivity to different onset asynchronies during a temporal order judgment task as a function of active stimulation relative to sham. While completing the task, participants were stimulated bilaterally for 20 min over either the TPJ or the human middle temporal area. We hypothesized that tRNS over the TPJ, which is critical to the temporal attention network, would selectively increase cortical excitability and induce cognitive training-like effects on performance, perhaps more so in the left visual field [Matthews, N., & Welch, L. Left visual field attentional advantage in judging simultaneity and temporal order. Journal of Vision, 15, 1–13, 2015; Romanska, A., Rezlescu, C., Susilo, T., Duchaine, B., & Banissy, M. J. High-frequency transcranial random noise stimulation enhances perception of facial identity. Cerebral Cortex, 25, 4334–4340, 2015]. In Experiment 1, we measured the performance of participants who judged the order of Gabors temporally imbedded in flickering discs, presented with onset asynchronies ranging from −75 msec (left disc first) to +75 msec (right disc first). In Experiment 2, we measured whether each participants temporal sensitivity increased with stimulation by using temporal offsets that the participant initially perceived as simultaneous. We found that parietal cortex stimulation temporarily increased sensitivity on the temporal order judgment task, especially in the left visual field. Stimulation over human middle temporal area did not alter cortical excitability in a way that affected performance. The effects were cumulative across blocks of trials for tRNS over parietal cortex but dissipated when stimulation ended. We conclude that single-session tRNS can induce temporary improvements in behavioral sensitivity and that this shows promising insight into the relationship between cortical stimulation and neural plasticity.

Unattended feature interference during a dynamic sequence task

Discrimination of features within temporal sequences affected by:-Rate of change of event (temporal frequency)-Presence of distracters-Salience of target features-Persistent features (color, orientation, etc.) easily discriminable Patterns of temporal transients are highly salient cues that promote perceptual