Distributed functions of prefrontal and parietal cortices during sequential categorical decisions

Comparing sequential stimuli is crucial for guiding complex behaviors. To understand mechanisms underlying sequential decisions, we compared neuronal responses in the prefrontal cortex (PFC), the lateral intraparietal (LIP), and medial intraparietal (MIP) areas in monkeys trained to decide whether sequentially presented stimuli were from matching (M) or nonmatching (NM) categories. We found that PFC leads M/NM decisions, whereas LIP and MIP appear more involved in stimulus evaluation and motor planning, respectively. Compared to LIP, PFC showed greater nonlinear integration of currently visible and remembered stimuli, which correlated with the monkeys’ M/NM decisions. Furthermore, multi-module recurrent networks trained on the same task exhibited key features of PFC and LIP encoding, including nonlinear integration in the PFC-like module, which was causally involved in the networks’ decisions. Network analysis found that nonlinear units have stronger and more widespread connections with input, output, and within-area units, indicating putative circuit-level mechanisms for sequential decisions.

Neural Processing of Cognitive Control in an Emotionally Neutral Context in Anxiety Patients

Impaired cognitive control plays a crucial role in anxiety disorders and is associated with deficient neural mechanisms in the fronto-parietal network. Usually, these deficits were found in tasks with an emotional context. The present study aimed at investigating electrophysiological and vascular signatures from event-related brain potentials (ERPs) and functional near-infrared spectroscopy (fNIRS) in anxiety patients versus healthy controls during an inhibition task integrated in an emotionally neutral context. Neural markers were acquired during the completion of a classical Eriksen flanker task. The focus of data analysis has been the ERPs N200 and P300 and fNIRS activations in addition to task performance. No behavioral or neural group differences were identified. ERP findings showed a larger N2pc and a delayed and reduced P300 for incongruent stimuli. The N2pc modulation suggests the reorienting of attention to salient stimuli, while the P300 indicates longer lasting stimulus evaluation processes due to increased task difficulty. FNIRS did not result in any significant activation potentially suggesting a contribution from deeper brain areas not measurable with fNIRS. The missing group difference in our non-emotional task indicates that no generalized cognitive control deficit but rather a more emotionally driven deficit is present in anxiety patients.

Ensemble Statistics Can Be Available before Individual Item Properties: Electroencephalogram Evidence Using the Oddball Paradigm

Behavioral studies have shown that statistical properties of object groups are perceived accurately with brief exposure durations. This finding motivated the hypothesis that ensemble perception occurs rapidly in vision. However, the precise timing of ensemble perception remains unclear. Here, we used the superior temporal resolution of electroencephalography to directly compare the timing of ensemble processing to that of individual object processing. The P3b was chosen as a particular component of interest, as it is thought to measure the latency of stimulus evaluation. Participants performed a simple “oddball” task in which sets of 51 lines with varied orientations sequentially flashed briefly on the display. In these sequences, there was a 20% chance of an individual oddball, wherein one marked object tilted clockwise, and a 20% chance of an ensemble oddball, wherein the average orientation of the set tilted 20% clockwise. In counterbalanced blocks, participants were instructed to respond to either individual or ensemble oddballs. ERP analysis was performed to test the timing of this processing. At parietal electrodes, P3b components were found for both individual and ensemble oddballs. Ensemble P3b components were found to occur significantly earlier than individual P3b components, as measured with both 50% area latency and 50% onset latency. Using multivariate pattern analysis, ensemble oddball trials were classifiable from standard trials significantly earlier in their timecourse than individual oddball trials. Altogether, these results provide compelling evidence that ensemble perception occurs rapidly and that ensemble properties can be available earlier than individual object properties.

A Functional Coupling of Brain and Behavior During Social Categorization of Faces

Considerable research has focused on how people derive information about others’ social category memberships from their faces. Theoretical models posit that early extraction of task-relevant information from a face should determine the efficiency with which that face is categorized, but evidence supporting this idea has been elusive. Here, we used a novel trial-level data analytic approach to examine the relationship between two event-related potential components—the P2, indexing early attention to category-relevant information, and the P3, indexing stimulus evaluation—and the speed of overt categorization judgments. As predicted, a larger face-elicited P2 on a particular trial was associated with faster overt race or gender categorization of that face. Moreover, this association was mediated by P3 latency, indicating that extraction of more category-relevant information early in processing facilitated stimulus evaluation. These findings support continuous flow models of information processing and the long-theorized functional significance of face-elicited neurophysiological responses for social categorization.

Experienced Category Variability Modulates the Impact of Context on Evaluative Judgments

Data from two experiments show that the experienced structure of a category (i.e., as having high vs. low variability) modulates the impact of context on evaluative judgments of individual exemplars. Target objects (unfamiliar in Experiment 1 and familiar in Experiment 2) were primed with positive and negative images while varying the number (Experiment 1) or typicity (Experiment 2) of exemplars known from a category prior to the judgment task. The results show that evaluations of object valence were more influenced by valenced context cues in high than in low variability category conditions. These results are taken as evidence that more varied exemplar-based category representations facilitate context effects on stimulus evaluation.