Stimulus Presentation Research Articles

MacBehaviour: An R package for behavioural experimentation on large language models

The study of large language models (LLMs) and LLM-powered chatbots has gained significant attention in recent years, with researchers treating LLMs as participants in psychological experiments. To facilitate this research, we developed an R package called “MacBehaviour “ (https://github.com/xufengduan/MacBehaviour), which interacts with over 100 LLMs, including OpenAI's GPT family, the Claude family, Gemini, Llama family, and other open-weight models. The package streamlines the processes of LLM behavioural experimentation by providing a comprehensive set of functions for experiment design, stimuli presentation, model behaviour manipulation, and logging responses and token probabilities. With a few lines of code, researchers can seamlessly set up and conduct psychological experiments, making LLM behaviour studies highly accessible. To validate the utility and effectiveness of “MacBehaviour,“ we conducted three experiments on GPT-3.5 Turbo, Llama-2-7b-chat-hf, and Vicuna-1.5-13b, replicating the sound-gender association in LLMs. The results consistently demonstrated that these LLMs exhibit human-like tendencies to infer gender from novel personal names based on their phonology, as previously shown by Cai et al. (2024). In conclusion, “MacBehaviour” is a user-friendly R package that simplifies and standardises the experimental process for machine behaviour studies, offering a valuable tool for researchers in this field.

Task-relevant stimulus design improves P300-based brain-computer interfaces.

In the pursuit of refining P300-based brain-computer interfaces (BCIs), our research aims to propose a novel stimulus design focused on selective attention and task relevance to address the challenges of P300-based BCIs, including the necessity of repetitive stimulus presentations, accuracy improvement, user variability, and calibration demands. In the oddball task for P300-based BCIs, we develop a stimulus design involving task-relevant dynamic stimuli implemented as finger-tapping to enhance the elicitation and consistency of event-related potentials (ERPs). We further improve the performance of P300-based BCIs by optimizing ERP feature extraction and classification in offline analyses. With the proposed stimulus design, online P300-based BCIs in 37 healthy participants achieve an accuracy of 91.2% and an information transfer rate (ITR) of 28.37 bits/min with two stimulus repetitions. With optimized computational modeling in BCIs, our offline analyses reveal the possibility of single-trial execution, showcasing an accuracy of 91.7% and an ITR of 59.92 bits/min. Furthermore, our exploration into the feasibility of across-subject zero-calibration BCIs through offline analyses, where a BCI built on a dataset of 36 participants is directly applied to a left-out participant with no calibration, yields an accuracy of 94.23% and the ITR of 31.56 bits/min with two stimulus repetitions and the accuracy of 87.75% and the ITR of 52.61 bits/min with single-trial execution. When using the finger-tapping stimulus, the variability in performance among participants is the lowest, and a greater increase in performance is observed especially for those showing lower performance using the conventional color-changing stimulus. Signficance. Using a novel task-relevant dynamic stimulus design, this study achieves one of the highest levels of P300-based BCI performance to date. This underscores the importance of coupling stimulus paradigms with computational methods for improving P300-based BCIs.

Stimulus conditions that promote habitual control

Two experiments in rats examined how training where a stimulus signaled when to respond for reward, conditions that should favour S-R learning, might lead to habitual control of behaviour. Experiment 1 investigated how animals trained with a stimulus preceding lever insertion would impact learning relative to a group that was self-paced and could control lever insertion with a second, distinct response. Rats were then tested for sensitivity to outcome devaluation to distinguish between goal-directed and habitual control. We found that free-operant, self-paced conditions promoted goal-directed control while signaling trials with a stimulus promoted habitual control evidenced as insensitivity to outcome devaluation. Experiment 2 assessed whether the stimulus-outcome association is important for driving habitual responding when training occurs with a traditional discriminative stimulus. A comparison group was trained under free-operant conditions and experienced the same stimulus presented alongside the earned reward. Following devaluation, animals trained under discriminated-operant conditions had reduced goal-directed control, but only after extended training. The free-operant group remained goal-directed, even after extended training, and their performance was not altered by stimulus presentations, suggesting effects of a stimulus-outcome association were unlikely to account for the deficit in the discriminative stimulus group. These results extend understanding of how stimuli present during instrumental training promote the development of habitual control.

The Influence of Light Colour on the Behaviour of Atlantic Cod in an Experimental Setting

Fishing technologies often exploit the visual sensitivity of target species to alter their behaviours. Atlantic cod (Gadus morhua Linnaeus, 1758) are an economically important species, commonly targeted by fisheries in the North Atlantic, yet the behaviour of adult Atlantic cod in reaction to the simultaneous presentation of various light stimuli has not been assessed in an isolated setting to determine if there is a preference for certain light qualities. To assess the influence that artificial light may have on the behaviour of Atlantic cod, we investigated the movement of wild-caught cod in a laboratory setting with green, blue, and white light with a blank control presented in paired choice tests. We predicted that green light would have the greatest influence on cod behaviour and that they would preferentially spend more time in proximity to that light condition. The findings show that cod behaved consistently across trials and across experimental sessions, and that the right side of the arena was preferred regardless of the colours of light presented. These findings indicate that cod do not prefer to spend more time in proximity to certain colours of light in an artificial environment, which has direct implications for animal husbandry, fisheries research, and behavioural ecology.

Healthy Aging is Associated with Altered Visual Gamma Band Onset and Offset Responses

Abstract Gamma oscillations have been shown to be critical for basic sensory processing, as well as visual attention and several other higher-order cognitive functions. Aberrant gamma oscillations have also been shown in neuropsychiatric and neurodegenerative diseases. Despite the possible clinical implications of altered gamma activity and emerging stimulation-based interventions targeting gamma, research into age-related changes in gamma oscillatory activity in healthy adults remains sparce. In the current study, we examined the neural oscillations underlying basic visual processing in 87 healthy aging adults using magnetoencephalography (MEG) and a visual grating stimulus. Neural activity elicited by the visual stimulus was imaged using a time-frequency resolved beamformer and peak voxel time series were computed to characterize the visual oscillatory dynamics underlying these responses. We found significant age-related changes in visual gamma oscillations, but not in visual theta, alpha, or beta oscillations. Specifically, we found age-related increases in gamma band amplitude and inter-trial phase-locking (ITPL) immediately following stimulus presentation (i.e., gamma onset response). Conversely, gamma band amplitude and ITPL following stimulus removal (i.e., gamma offset response) were found to be decreased as a function of healthy aging. Critically, we demonstrated that the decreases in the gamma offset response predicted slower overall processing speed across all participants. Taken together, these findings indicate that healthy aging is uniquely associated with alterations in visual gamma oscillations and that these changes predict participant processing speed.

Maintenance of Bodily Expressions Modulates Functional Connectivity Between Prefrontal Cortex and Extrastriate Body Area During Working Memory Processing

Background/Objectives: As a form of visual input, bodily expressions can be maintained and manipulated in visual working memory (VWM) over a short period of time. While the prefrontal cortex (PFC) plays an indispensable role in top-down control, it remains largely unclear whether this region also modulates the VWM storage of bodily expressions during a delay period. Therefore, the two primary goals of this study were to examine whether the emotional bodies would elicit heightened brain activity among areas such as the PFC and extrastriate body area (EBA) and whether the emotional effects subsequently modulate the functional connectivity patterns for active maintenance during delay periods. Methods: During functional magnetic resonance imaging (fMRI) scanning, participants performed a delayed-response task in which they were instructed to view and maintain a body stimulus in working memory before emotion categorization (happiness, anger, and neutral). If processing happy and angry bodies consume increased cognitive demands, stronger PFC activation and its functional connectivity with perceptual areas would be observed. Results: Results based on univariate and multivariate analyses conducted on the data collected during stimulus presentation revealed an enhanced processing of the left PFC and left EBA. Importantly, subsequent functional connectivity analyses performed on delayed-period data using a psychophysiological interaction model indicated that functional connectivity between the PFC and EBA increases for happy and angry bodies compared to neutral bodies. Conclusions: The emotion-modulated coupling between the PFC and EBA during maintenance deepens our understanding of the functional organization underlying the VWM processing of bodily information.

Sensitization and Habituation of Hyper-Excitation to Constant Presentation of Pattern-Glare Stimuli.

Pattern glare, associated with cortical hyperexcitability, induces visual distortions and discomfort, particularly in individuals susceptible to migraines or epilepsy. While previous research has primarily focused on transient EEG responses to patterned stimuli, this study aims to investigate how continuous presentation of pattern-glare stimuli affects neural adaptation over both fine (seconds) and coarse (entire experiment) temporal scales. EEG recordings were obtained from 40 healthy participants exposed to horizontal square-wave gratings at three spatial frequencies presented continuously for three seconds each across multiple trials. Participants' susceptibility to visual stress, headaches, and discomfort was assessed using questionnaires before and during the experiment. The experiment employed a two-by-two design to evaluate habituation (exponentially decreasing response) and sensitisation (exponentially increasing response) effects at two different time granularities. Mass univariate analysis with cluster-based permutation tests was conducted to identify significant brain response changes during the period of constant stimulation, which we call the DC-shift period. Significant effects were observed during the DC-shift period, indicating sustained hyper-excitation to the medium-pattern glare stimulus. In particular, the mean/intercept analysis revealed a consistent positive-going response to the medium stimulus throughout the DC-shift period, suggesting continued neural engagement. Participants reporting higher discomfort exhibited sensitisation at fine temporal granularity and habituation at coarser temporal granularity. These effects were predominantly localised to the right posterior scalp regions. The study demonstrates that individuals sensitive to pattern-glare stimuli exhibit dynamic neural adaptation characterised by short-term sensitisation and long-term habituation. These findings enhance the understanding of cortical hyperexcitability mechanisms and may inform future interventions for visual-stress-related conditions, such as migraines and epilepsy. Further research is needed to explore the underlying neural processes and validate these effects in clinical populations.

Multitasking, an EEG experiment: comparative analysis of cognitive workload during demanding stimuli presentation

Multitasking, an EEG experiment: comparative analysis of cognitive workload during demanding stimuli presentation

Different effects of smooth pursuit eye movements on motion-based stimulus response congruency.

In the motion-based stimulus-response compatibility (SRC) effect, responses are faster when the task-irrelevant stimulus motion is congruent with the response movement performance. In the present study, we tested whether smooth pursuit eye movements, related to tracking a moving object, influence motion-based SRC when present on their own or when combined with position-based SRC. We examined the motion-based SRC effect during both the response selection and response execution stages. When investigating motion-based SRC alone, participants responded with left or right movements of the single hand to the left or right movements of a centrally presented stimulus, either with their eyes fixated at the center or tracking the moving object. In the case of combined motion-based and position-based SRC, participants responded with left or right movements of the left or right hand to stimulus motion presented on the left or right side of the screen, again with eyes either fixated at the center or following the moving target. Results showed that during the response selection stage, smooth pursuit type eye movements had no effect on the motion-based SRC when the stimulus moved in the center, whereas the effect was enhanced when the stimulus presentation was lateralized. This aligns with the idea that attentional shifts differ between central and peripheral vision and that cognitive system computes various spatial maps for stimulus and response. In the case of response execution, smooth pursuit type eye movements had no effect on the motion-based SRC effect, regardless of stimulus location.

Timing matters: investigating the interplay of presentation duration and congruency in approximate number processing.

The approximate number system (ANS) is an innate number sense ability; it plays a pivotal role in the development of symbolic number ability. Despite studies using a wide range of presentation durations of stimuli to investigate the approximate number processing, limited literature has systematically explored its impact on approximate number processing. Further, if increasing presentation duration leads to improved accuracy, it remains unclear whether this improvement will be driven by better performance in both congruent and incongruent conditions or only in one condition. Addressing these gaps, the present study investigated the impact of presentation duration on the approximate number processing among 45 college-going adult participants from India. The dot number comparison task was used to measure ANS, with stimuli presentation duration manipulated at the following durations: 100, 200, 500, 1000, and 3000 milliseconds (or until response). Based on the congruency of non-numerical features of dots with numerosity of dots, trials were categorized into congruent and incongruent trials. Repeated measure ANOVA revealed a positive relationship between the presentation duration and dot number comparison accuracy. However, a saturation point in performance was observed at a presentation duration of 500 milliseconds, beyond which increased duration did not lead to enhanced accuracy. Further analysis based on congruency revealed that performance improvement was confined only to congruent conditions. Drawing on samples from India, the study offers valuable insights into the ANS.

Pupil size correlates with heart rate, skin conductance, pulse wave amplitude, and respiration responses during emotional conflict and valence processing.

Pupil size is a non-invasive index for autonomic arousal mediated by the locus coeruleus-norepinephrine (LC-NE) system. While pupil size and its derivative (velocity) are increasingly used as indicators of arousal, limited research has investigated the relationships between pupil size and other well-known autonomic responses. Here, we simultaneously recorded pupillometry, heart rate, skin conductance, pulse wave amplitude, and respiration signals during an emotional face-word Stroop task, in which task-evoked (phasic) pupil dilation correlates with LC-NE responsivity. We hypothesized that emotional conflict and valence would affect pupil and other autonomic responses, and trial-by-trial correlations between pupil and other autonomic responses would be observed during both tonic and phasic epochs. Larger pupil dilations, higher pupil size derivative, and lower heart rates were observed in the incongruent condition compared to the congruent condition. Additionally, following incongruent trials, the congruency effect was reduced, and arousal levels indexed by previous-trial pupil dilation were correlated with subsequent reaction times. Furthermore, linear mixed models revealed that larger pupil dilations correlated with higher heart rates, higher skin conductance responses, higher respiration amplitudes, and lower pulse wave amplitudes on a trial-by-trial basis. Similar effects were seen between positive and negative valence conditions. Moreover, tonic pupil size before stimulus presentation significantly correlated with all other tonic autonomic responses, whereas tonic pupil size derivative correlated with heart rates and skin conductance responses. These results demonstrate a trial-by-trial relationship between pupil dynamics and other autonomic responses, highlighting pupil size as an effective real-time index for autonomic arousal during emotional conflict and valence processing.

NCOG-32. RELATIONSHIPS BETWEEN INTRAOPERATIVE TASK-BASED GAMMA BAND ELECTROCORTICOGRAMS, DIRECT ELECTRICAL STIMULATION, AND COGNITIVE-LINGUISTIC OUTCOME FOLLOWING AWAKE BRAIN TUMOR RESECTION

Abstract BACKGROUND As an adjunct to direct electrical stimulation (DES), intraoperative electrocorticography (ECoG) can aid detection of language-eloquent cortex. However, it is unclear how surgical impact upon mapping findings relates to cognitive-linguistic outcomes. METHODS Ten patients underwent awake craniotomy for tumor resection with ECoG and DES language mapping. Mapping utilized iPad stimulus presentation coupled to an electrode array capable of both recording ECoG activity and delivering DES. Time-frequency gamma band activations were visualized (Early, Long, Late, Double Peak) for 3 naming paradigms (Object, Action, Auditory). DES was also conducted for each task. Mapping results were overlayed on postoperative MRI to examine proximity to parenchymal trauma (cavity, sulcal displacement). Patients completed cognitive-linguistic testing [WAB-R (N=3) or Neuropsychological Assessment (N=7)] prior to surgery and <2 months postoperatively. Patients with persisting aphasia at 6-month follow-up were also identified. RESULTS Postoperative language decline was found in 50% of patients, with 30% showing worsening (>1SD) in Naming and Phonemic Fluency, and 60% in Semantic Fluency. Surgery impacted ECoG features in 60% of patients and DES arrest sites in 30%. A trend was observed where Early and Late Object naming ECoG features were associated with Semantic Fluency decline [rpb(5)=-.69, p=.067]. Arrest during Auditory naming DES <1 cm of surgical effect was associated with decline in Abstraction [rpb(5)=-.83, p=.042; FET, p=.029] and Semantic Fluency [rpb(5)=-.87, p=.012; FET, p=.024]. Excluding the 3 transsulcal surgeries, arrest during Auditory naming DES <1 cm of resection was associated with general language decline [FET, p=.047]. All 3 patients with persisting aphasia had Auditory naming arrest <1 cm of resection and 2/3 patients had Object naming ECoG features resected. CONCLUSIONS While preliminary, results suggest that surgical proximity to ECoG and DES mapping results may inform risk of surgically-acquired cognitive-linguistic decline. Findings support the potential of multimethod-multitask intraoperative language mapping.

Hemispheric asymmetry for global-local processing: Effects of stimulus category and ageing.

Hemispheric asymmetry has been reported for global-local processing in young and older adults, with global processing specialised in the right hemisphere (RH-global specialisation) and local processing specialised in the left hemisphere (LH-local specialisation). Questions persist regarding the extent to which hemispheric asymmetry is influenced by stimulus category (verbal stimuli processed in the left hemisphere; visuospatial stimuli processed in the right hemisphere). Some evidence suggests stimulus category does not influence hemispheric asymmetry (stimulus-independent account) while other evidence suggests it does (stimulus-dependent account). In older adults, there is evidence of a local-processing advantage, believed to result from slower and less accurate performance in right-hemisphere compared to left-hemisphere functioning-the right-hemisphere ageing hypothesis. We examined hemispheric asymmetry for global-local processing in young and older participants with three hierarchical figures (letters, verbalisable objects, and nonverbalisable shapes), in a within-subjects design using a divided-attention paradigm and unilateral presentation. Our findings for letters and verbalisable objects support the stimulus-independent account-young and older participants demonstrated RH-global specialisation and LH-local specialisation regardless of stimulus category. In older participants, we also found a local-processing advantage for all three stimulus categories-an advantage best explained as faster and more accurate performance in local processing regardless of the visual field of stimulus presentation. Overall, we found hemispheric asymmetry for global-local processing in both young and older adults, and differences in global processing between young and older adults. Future investigation is suggested for the hemispheric asymmetry found in global-local processing of nonverbalisable shapes, and the mechanisms underlying age-related changes in global processing.

NCOG-34. CORRESPONDENCE BETWEEN INTRAOPERATIVE GAMMA BAND ELECTROCORTICOGRAMS AND DIRECT ELECTRICAL STIMULATION ACROSS DIVERSE NAMING TASKS IN PATIENTS WITH LANGUAGE-ELOQUENT BRAIN TUMORS

Abstract BACKGROUND Few studies have examined concordance between intraoperative electrocorticography (ECoG) and direct electrical stimulation (DES) language mapping, especially across varied naming tasks. METHODS Twelve patients (Mdn age=59; 75% HGG) underwent awake craniotomy with ECoG and DES language mapping. Mapping utilized iPad stimulus presentation coupled to a 4x8 electrode array for both ECoG and DES. Time-frequency ECoG gamma band activity (Early and Late) was visualized for 3 naming paradigms (Object, Action, Auditory). Bipolar DES was also conducted for each task at each electrode pair. ECoG activations and DES hits were overlayed on preoperative MRI. DES hits represented ground truth for eloquence. ECoG accuracy was examined for each task with 3 different criteria: exact (identical electrodes for ECoG activation and DES hits), adjacent (ECoG <1cm of DES hits), and adjacent within a predefined peritumoral region of interest (<2 cm from boundaries). RESULTS 32 DES hits (40% Auditory, 32% Action, 28% Obj) were observed across patients. Exact ECoG-DES accuracy ranged from 78%-90% [Object: Sens=11%, Spec=91%, PPV=6%, NPV=95%; Action: Sens=40%, Spec=93%, PPV=24%, NPV=97%; Auditory: Sens=69%, Spec=78%, PPV=19%, NPV=78%]. Adjacent ECoG-DES accuracy ranged from 82%-91% [Object: Sens=33%, Spec=92%, PPV=18%, NPV=97%; Action: Sens=44%, Spec=93%, PPV=25%, NPV=97%; Auditory: Sens=91%, Spec=81%, PPV=37%, NPV=99%]. When restricted to the peritumoral region, adjacent ECoG-DES accuracy ranged from 94%-97% [Object: Sens=14%, Spec=99%, PPV=25%, NPV=97%; Action: Sens=25%, Spec=99%, PPV=25%, NPV=99%; Auditory: Sens=100%, Spec=94%, PPV=54%, NPV=100%]. For patients with DES hits (N=10), all had at least 1 task activation <1 cm of DES hits, with 7/10 having convergence of activations across at least 2 tasks. CONCLUSIONS Negative ECoG mapping is strongly predictive of non-eloquence confirmed by DES for all naming tasks. Additionally, gamma band activation elicited by auditory naming within the peritumoral region is strongly predictive of eloquence. Findings support task-based ECoG language mapping for prediction of eloquence and identification of targets for DES confirmation.

Reconsidering Divergent and Convergent Thinking in Creativity – a Neurophysiological Index for the Convergence-Divergence Continuum

ABSTRACT Creative problem-solving has been described as an iterative process of divergent and convergent modes of thinking. With this opinion paper, we illustrate how some tasks, commonly used for the neuroscientific investigation of creativity might provide a condensed representation of divergent and convergent thinking, respectively. We have identified the following reasons for this: The specific presentation of stimuli and response alternatives within these tasks (“immediate problem space accessibility”), the restricted time on task for participants in well-established creativity tasks, as well as the challenges to identify specific temporal dynamics of divergent-convergent cycles using standard EEG procedures. Based on two recent studies, we propose that upper alpha band (10–12 hz) modulations in particular may serve a) as a neuro-physiological index to disentangle divergent-convergent cycles within these creativity tasks and b) as a data-driven marker for the task demands related to immediate problem space accessibility. Finally, we argue for a view on divergent and convergent thinking that is less of a dichotomy and more of a continuum.

Сенсомоторна реакція представників ігрових видів спорту при різній моторній відповіді на подразники

Smoothing or emphasizing on laterality of movements in athletes depends on the specifics of the sport and determining perceptual-motor abilities. Individual motor features. Their consideration in the process of sports training is impossible without knowledge of the presence and degree of manifestation of motor asymmetry, which will affect the sports result. Objective: to establish the peculiarities of sensorimotor response of athletes of game sports in comparison with representatives of cyclic sports and martial arts at different motor response to stimuli. Material and methods: student-athletes of game, cyclic sports and martial arts at the age of 18-23 years were studied. The study was conducted according to the diagnostic training method ReactionX: sensorimotor response to audiosensory stimuli of Standard and Sequence programs in Close and Far distance conditions. Results: data of sensorimotor reaction of representatives of game, cyclic sports and martial arts in different conditions of stimuli presentation and motor response were obtained. Separate comparisons of indicators of sensorimotor component of readiness by reaction speed and perceptual-cognitive component by the number of processed signals of representatives of game sports with other groups of athletes were made. The statistical reliability of comparison of the studied parameters is shown and the value of the difference of indicators is presented. Conclusions: the peculiarities of the sensorimotor response of representatives of game sports consisted in a higher speed of response and a greater number of perceived and processed signals at a remote response with the right (dominant) hand in the program of random stimulus presentation. In contrast, the peculiarity of sensorimotor reaction of representatives of cyclic sports and martial arts was the highest number of perceived and processed signals at a remote response with the right hand in the program with a sequential order of presentation of signals. Perceptual-motor symmetry was found in athletes, regardless of specialization, when responding to the sequential order of appearance of signals as opposed to their arbitrary presentation.

Effects of Vergence Eye Movement Planning on Size Perception and Early Visual Processing.

Our perception of objects depends on non-oculomotor depth cues, such as pictorial distance cues and binocular disparity, and oculomotor depth cues, such as vergence and accommodation. Although vergence eye movements are always involved in perceiving real distance, previous studies have mainly focused on the effect of oculomotor state via "proprioception" on distance and size perception. It remains unclear whether the oculomotor command of vergence eye movement would also influence visual processing. To address this question, we placed a light at 28.5 cm and a screen for stimulus presentation at 57 cm from the participants. In the NoDivergence condition, participants were asked to maintain fixation on the light regardless of stimulus presentation throughout the trial. In the WithDivergence condition, participants were instructed to initially maintain fixation on the near light and then turn their two eyes outward to look at the stimulus on the far screen. The stimulus was presented for 100 msec, entirely within the preparation stage of the divergence eye movement. We found that participants perceived the stimulus as larger but were less sensitive to stimulus sizes in the WithDivergence condition than in the NoDivergence condition. The earliest visual evoked component C1 (peak latency 80 msec), which varied with stimulus size in the NoDivergence condition, showed similar amplitudes for larger and smaller stimuli in the WithDivergence condition. These results show that vergence eye movement planning affects the earliest visual processing and size perception, and demonstrate an example of the effect of motor command on sensory processing.

Evaluating prefrontal changes in depression using functional near-infrared spectroscopy utilizing Stroop test: A comparison with healthy controls

Background: Functional near-infrared spectroscopy (fNIRS) is being increasingly utilized to visualize the brain areas involved in cognitive activity to understand the human brain better. Its portability and easy setup give it an advantage over other functional brain imaging tools. The current study utilizes fNIRS while performing a Stroop test, which is commonly used to assess the impairment of information selection in depression. Aim: To compare cortical activation during the Stroop test in depressed individuals to healthy controls. Methods: This cross-sectional study compared oxyhemoglobin (OxyHb) concentration changes in 39 individuals with depression to 40 healthy individuals. The Stroop test was construed in an event-related design with an intertrial interval of 2 seconds with jitter. A continuous wave fNIRS system was used for recording the cortical activity at 17 locations. Analysis of fNIRS data was done using statistical parametric mapping (SPM) for estimating general linear model (GLM) coefficients. Further analysis of the mean change of OxyHb concentrations during the 2 seconds after the presentation of congruent and incongruent stimuli was done between the groups using Mann–Whitney U test corrected for multiple comparisons with Bonferroni correction. Results: While the number of errors and correct responses were similar between the groups, the reaction time for correct responses was more in the depression group in comparison to healthy individuals (t = -2.39, P = 0.01). For both healthy and depressive individuals in incongruent versus congruent task contrast, deactivation was seen in the region between the left middle frontal sulcus and frontopolar area of the brain (t = 0.41 and t = 0.21, respectively, P < 0.05). The depressed group had a higher mean change in OxyHb concentration following incongruent stimuli in comparison to the HCs (mean rank: HC = 32.63, depression = 47.56). Conclusion: Our findings indicate that individuals with depression exhibited prolonged reaction times and distinct activation patterns of the frontal cortex compared to healthy individuals. The observed pattern of brain activation for congruent and incongruent tasks among both healthy and depressed individuals aligns with the findings of the prior studies, emphasizing the utility of fNIRS as a valuable instrument for assessing brain activity.

The sustenance and retention of perspectival shape representations

When we are presented with a coin rotated in depth, although we perceive its objective circular shape, the original perspectival shape is nonetheless represented in the visual system. Here we investigated the onset time and duration of such perspectival representation by systematically manipulating stimuli presentation time vs. post-stimuli retention time. Participants performed a speeded search task and had to find an oval target against a circle distractor that is either head-on (i.e., perspectivally dissimilar) or rotated leftward/rightward (i.e., perspectivally similar). We found that even when stimuli disappeared from view, participants still took more time in locating the oval target, suggesting robust and persistent perspectival interference (Experiment 1). This interference emerged as early as 100 ms (Experiment 2), and persisted for at least 1000 ms (Experiment 3). Together, these results suggest a 100 ms formation time and possibly 1000 ms or longer life span for perspectival representation.

Symmetrical choices and biased confidence during uncertain personality trait judgments.

While great methodological strides have been made in the area of decision making research, decisions that rely on subjective stimuli, such as personality traits, still pose a challenge for researchers, partly because it is difficult to define a standard of accuracy for such choices-they lack a "ground truth". In studies on value-based decisions, this same problem has been circumvented by comparing uncertain subjective decisions against a separately assessed judgment of value-a "standard". Here we apply this method in a task of verbal personality trait judgment, and show how a separately assessed standard judgment can be used to precisely control stimulus presentation and analyze subjective personality choices via the method of reverse correlation. Per trial, a series of quasi-randomly sampled adjectives was shown, which participants categorized as more descriptive of either themselves of another person well known to them. Participants also indicated their confidence in the response. Each trial's difficulty was controlled based on the previously assessed standard judgment. Analysis of the behavioral data shows several decision-general properties during these personality judgments, such as symmetrical choices, steeper choice functions for confident trials, and a positive evidence bias during confidence judgment. We discuss how these findings can shed light on the cognitive processes involved in personality perception. The task and results together may help bridge the gap between research on complex, social forms of judgment and findings on more basic decision processes.