A cortical substrate for the long-term memory of saccadic eye movements calibration

The roles of the LpSTS and DLPFC in self-prioritization: A transcranial magnetic stimulation study

The Self‐Attention Network (SAN) has been proposed to describe the underlying neural mechanism of the self‐prioritization effect, yet the roles of the key nodes in the SAN—the left posterior superior temporal sulcus (LpSTS) and the dorsolateral prefrontal cortex (DLPFC)—still need to be clarified. One hundred and nine participants were randomly assigned into the LpSTS group, the DLPFC group, or the sham group. We used the transcranial magnetic stimulation (TMS) technique to selectively disrupt the functions of the corresponding targeted region, and observed its impacts on self‐prioritization effect based on the difference between the performance of the self‐matching task before and after the targeted stimulation. We analyzed both model‐free performance measures and HDDM‐based performance measures for the self‐matching task. The results showed that the inhibition of LpSTS could lead to reduced performance in processing self‐related stimuli, which establishes a causal role for the LpSTS in self‐related processing and provide direct evidence to support the SAN framework. However, the results of the DLPFC group from HDDM analysis were distinct from the results based on response efficiency. Our investigation further the understanding of the differentiated roles of key nodes in the SAN in supporting the self‐salience in information processing.

Saccadic adaptation shapes perceived size: Common codes for action and perception

Recent findings suggest that perceptual and motor systems share common codes; for instance, perceived object location is known to correlate with motor changes in the oculomotor system. Here, we investigate whether modifying saccade amplitude affects object size perception. Participants saw in peripheral vision a test disk that could vary in size across trials. This disk was then replaced by a small target cross, which was the signal to make a saccade. After the saccade, the target cross was extinguished and replaced by a reference disk (thus seen in foveal vision). Participants had to compare the post- to the pre-saccade disk sizes. Psychometric functions were obtained before and after one session of 142 saccades made toward the cross that either stepped toward the fixation point during the saccade (backward adaptation group) or remained stationary (control group). In the experimental group, stepping the target cross toward fixation during saccades decreased movement amplitude, a phenomenon called saccadic adaptation. We observed a concurrent shift in the psychometric functions reflecting a decrease in perceived object size. Such a perceptual modification did not occur in the control group. Our results reveal that motor changes co-occur with changes in perceived object size. Unlike previous studies evaluating the impact of saccadic adaptation on perceived location, we measured here the perception of another spatial feature (the object size) that is not relevant for the sensorimotor transformation. Theoretical implications of the strong links between oculomotor parameters and object perception are discussed.

Inducing oculomotor plasticity to disclose the functional link between voluntary saccades and endogenous attention deployed perifoveally

To what extent oculomotor and attention systems are linked remains strongly debated. Previous studies suggested that saccadic adaptation, a well-studied model of oculomotor plasticity, and orienting of attention rely on overlapping networks in the parietal cortex and can functionally interact. Using a Posner-like paradigm in healthy human subjects, we demonstrate for the first time that saccadic adaptation boosts endogenous attention orienting. Indeed, the discrimination of perifoveal targets benefits more from central cues after backward adaptation of leftward voluntary saccades than after a control saccade task. We propose that the overlap of underlying neural networks actually consists of neuronal populations co-activated by oculomotor plasticity and endogenous attention deployed perifoveally. The functional coupling demonstrated here plaids for conceptual models not belonging to the framework of the premotor theory of attention as the latter has been rejected precisely for this voluntary/endogenous modality. These results also open new perspective for rehabilitation of visuo-attentional deficits.

Saccadic Adaptation Boosts Ongoing Gamma Activity in a Subsequent Visuoattentional Task

Attention and saccadic adaptation (SA) are critical components of visual perception, the former enhancing sensory processing of selected objects, the latter maintaining the eye movements accuracy toward them. Recent studies propelled the hypothesis of a tight functional coupling between these mechanisms, possibly due to shared neural substrates. Here, we used magnetoencephalography to investigate for the first time the neurophysiological bases of this coupling and of SA per se. We compared visual discrimination performance of 12 healthy subjects before and after SA. Eye movements and magnetic signals were recorded continuously. Analyses focused on gamma band activity (GBA) during the pretarget period of the discrimination and the saccadic tasks. We found that GBA increases after SA. This increase was found in the right hemisphere for both postadaptation saccadic and discrimination tasks. For the latter, GBA also increased in the left hemisphere. We conclude that oculomotor plasticity involves GBA modulation within an extended neural network which persists after SA, suggesting a possible role of gamma oscillations in the coupling between SA and attention.