Psychophysics

In this fMRI study we investigated functional connectivity between components of the mentalising system during a social emotion task, using psychophysiological interaction (PPI) analysis. Ten adults (22–32 years) and 18 adolescents (11–18 years) were scanned while thinking about scenarios in which a social or a basic emotion would be experienced. Unlike basic emotions (such as disgust and fear), social emotions (such as embarrassment and guilt) require the representation of another’s mental states. In both adults and adolescents, an anterior rostral region of medial prefrontal cortex (arMPFC) involved in mentalising showed greater connectivity with the posterior superior temporal sulcus (pSTS) bordering on the temporo-parietal junction (TPJ) and with anterior temporal cortex (ATC) during social than during basic emotion. This result provides novel evidence that components of the mentalising system interact functionally during a social emotion task. Furthermore, functional connectivity differed between adolescence and adulthood. The adolescent group showed stronger connectivity between arMPFC and pSTS/TPJ during social relative to basic emotion than did the adult group, suggestive of developmental changes in functional integration within the mentalising system.

The two contrasting theoretical approaches to visual perception, the constructivist and the ecological, are briefly presented and illustrated through their analyses of space and size perception. Earlier calls for their reconciliation and unification are reviewed. Neurophysiological, neuropsychological, and psychophysical evidence for the existence of two quite distinct visual systems, the ventral and the dorsal, is presented. These two perceptual systems differ in their functions; the ventral system's central function is that of identification, while the dorsal system is mainly engaged in the visual control of motor behavior. The strong parallels between the ecological approach and the functioning of the dorsal system, and between the constructivist approach and the functioning of the ventral system are noted. It is also shown that the experimental paradigms used by the proponents of these two approaches match the functions of the respective visual systems. A dual-process approa...

This Lab aims at:

1. The clinical consolidation of the Quanto-Geometric Psychophysics Framework of the Human Mental thru the establishment of a data acquisition and experimental platform.

2. The eventual development of mental health and clinical practice products arising from the visualizations, methodologies and solutions brought about by the Theory.

The sum of the Theory is exposed in the publication Functional Architecture of the Human Mental, ISBN 978-0-9647466-8-8, co-authored by Joseph J. Jean-Claude, Laser-Optics Associate Engineer, and Caroline Stamu-O’Brien, MD.

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Humans’ conscious awareness of objects in their visual periphery is limited. This limit is not entirely the result of reduced visual acuity. Rather, it is primarily caused by crowding—the difficulty identifying an object when it is surrounded by clutter. The effect of crowding on visual awareness in infants has yet to be explored. Do infants, for example, have a fine-grained “spotlight,” as adults do, or do infants have a diffuse “lantern” that sets limits on what they can register in their visual periphery? We designed an eye-tracking paradigm to psychophysically measure crowding in infants between 6 months and 15 months of age. We showed infants pairs of faces at three eccentricities, in the presence or absence of flankers, and recorded infants’ first saccade from central fixation to either face. Infants could discriminate faces in the periphery, and flankers impaired this ability. We found that the effective spatial resolution of infants’ visual perception increased with age, but...

We combined a prototypical exogenous cuing procedure with rapid serial visual presentation (RSVP) to provide a precise characterization of the temporal dynamics of reflexive attention shifts. The novel paradigm thus created has several useful properties, most notably that the physical presentation of the target is neither an onset nor a unique event and that temporal precision is provided without the requirement for a speeded response. A biphasic pattern was observed, with early benefits followed by later costs (inhibition of return) at the cued location relative to the uncued location. The finding of inhibition of return in this paradigm disproves the assertion that inhibition of return is merely a reluctance to respond in the target's direction. It may be partly that, but encoding mechanisms linked to attention must also be involved.

In general, information about the environment (for instance a target) is not instantaneously available for the nervous system. A minimal delay for visual information to affect the movement of the hand is about 110 ms. However, if the movement of a target is predictable, humans can pursue it with zero delay. To make this prediction, information about the speed of the target is necessary. Our results show that this information is used with a delay of about 200 ms. We discuss that oculomotor efference is a likely source of information for this prediction.

The Fourier phase spectrum plays a central role regarding where in an image contours occur, thereby defining the spatial relationship between those structures in the overall scene. Only a handful of studies have demonstrated
psychophysically the relevance of the Fourier phase spectrum with respect to human visual processing, and none have demonstrated the relative amount of local cross-scale spatial phase alignment needed to perceptually
extract meaningful structure from an image. We investigated the relative amount of spatial phase alignment needed for humans to perceptually match natural scene image structures at three different spatial frequencies [3, 6, and 12 cycles per degree (cpd)] as a function of the number of structures within the image (i.e., “structural sparseness”). The results showed that (1) the amount of spatial phase alignment needed to match structures depends on structural sparseness, with a bias for matching structures at 6 cpd and (2) the ability to match partially phase-randomized images at a given spatial frequency is independent of structural sparseness at other spatial frequencies. The findings of the current study are discussed in terms of a network of feature integrators in the human visual system.

Historically, taste research has often been guided by the concept that there are only four (or possibly five) basic taste qualities (sweet, sour, salty, and bitter, and possibly "umami"). All other tastes have been presumed to be combinations of these basic tastes. This psychophysical concept has been extended to electrophysiological data. That is, the neural code for each basic taste is hypothesized to be coded by a dedicated channel of neurons (the "Labeled-Line" theory); i.e., one group of neurons signals "salty" and another separate group signals "sweet." Numerous psychophysical and electrophysiological findings, however, cannot be accomodated by this quadripartite theory, which limits taste to four basic qualities and four basic neuron types. Rather, the data described in this article suggest that the range of taste is more extensive than four or five basic tastes, and that this breadth of taste quality results initially from the activati...

False working memories readily emerge using a visual item-recognition variant of the converging associates task. Two experiments, manipulating study and test modality, extended prior working memory results by demonstrating a reliable false recognition effect (more false alarms to associatively related lures than to unrelated lures) within seconds of encoding in either the visual or auditory modality. However, false memories were nearly twice as frequent when study lists were seen than when they were heard, regardless of test modality, although study-test modality mismatch was generally disadvantageous (consistent with encoding specificity). A final experiment that varied study-test modality using a hybrid short- and long-term memory test (Flegal, Atkins & Reuter-Lorenz, 2010) replicated the auditory advantage in the short term but revealed a reversal in the long term: The false memory effect was greater in the auditory study-test condition than in the visual study-test condition. Th...

From Dissociation to System: The Concept of the Unconscious as a Descendant of the Reflex Paradigm in Freud. The paper tries to situate Freud's theory historically by referring it to a paradigm of psychological theory that Marcel Gauchet describes as the “Golden Age” of psychophysics and reflex theory, and that he situates between 1870 and 1900. I will show that until 1900 Freud thinks, in fact, in categories that correspond to this type of thought. His texts On the Psychical Mechanism of Hysterical Phenomena (1893, with Josef Breuer) and A Project for a Scientific Psychology (1895) still follow the conception of a psychological subject on the basis of the stimulus and response model, which can be found in numerous contemporaneous authors. In this model, the psyche is just a place of transit open to the exterior, and its unity can only be a sum of elements of consciousness having a physiological substrate. Nevertheless, Freud's early texts – although appertaining to the reflex paradigm – already contain elements that serve to construct another basic model of the psychic apparatus, which is finally introduced by The Interpretation of Dreams. Those new elements are the separation between interior and exterior, the introduction of endogenous energy, which is linked to the importance of emotions instead of sensations, and the problem of the adaptation to outer reality that results from it. Nevertheless, once more Freud is not the only theorist in whose thought the new paradigm can be found; I again refer his new premises to other contemporary psychologists. The question that arises from Freud's passage from one paradigm to another is how he handles the continuity of his own thought. I describe the difficult compromise between contradictory concepts he finds in his Project for a Scientific Psychology; but certain concepts that derive from the reflex paradigm subsist even during the later development of psychoanalysis. This is especially the case for the concept of the unconscious itself: As I argue, this concept originates in the reflex paradigm, and, in contrast to contemporary psychology, Freud only maintains it longer than other authors do.

We investigated how does the structure of empty time intervals influence temporal processing. In experiment 1, the intervals to be discriminated were the silent durations marked by two sensory signals, both lasting 10 or 500 ms; these signals were two identical flashes (intramodal: VV), or one visual flash (V) followed by an auditory tone (A) (intermodal: VA). For the range of duration under investigation (standards = 0.2, 0.6, 1, or 1.4 s), the results indicated that both the marker length and sensory mode influenced discrimination, but no interaction between these variables or between one of these variables and standard duration was significant. In experiment 2, we compared, for each of four marker-type conditions (VV, AA, VA, AV; and standard = 1 s), intervals marked by two 10 ms signals with intervals marked by unequal signal length (markers 1 and 2 lasting 10 and 500 ms, or 500 and 10 ms). As in experiment 1, the results revealed significant marker-mode and marker-length effects, but no significant interaction between these variables. Experiment 3 showed that, for the same conditions as in experiment 2, perceived duration is not influenced by marker length and that the variability of interval reproductions does not depend on the perceived duration of intervals. The results are discussed in the light of a single-clock hypothesis: marker-length and marker-mode effects are presented as being non-temporal sources of variability associated mainly with sensory and memory processes.

The study of human behaviour ultimately requires the documentation of human movement. In some instances movements can be recorded through a simple button press on a computer input device. In other situations responses can be captured through questionnaire surveys. Nevertheless, there is a need within many neuroscience settings to capture how complex movements unfold over time (human kinematics). Current methods of measuring human kinematics range from accurate but multifarious laboratory configurations to ...