The mechanism underlying inhibition of saccadic return

Human observers take longer to re-direct gaze to a previously fixated location. Although there has been some exploration of the characteristics of inhibition of saccadic return (ISR), the exact mechanisms by which ISR operates are currently unknown. In the framework of accumulation models of response times, in which evidence is integrated over time to a response threshold, ISR could reflect a reduction in the rate of accumulation for saccades to return locations or an increase in the effective criterion for response. In two experiments, participants generated sequences of three saccades, in response to a peripheral or a central cue. ISR occurred across these manipulations: saccade latency was consistently increased for movements to the immediately previously fixated location. Latency distributions from individual observers were fit with a Linear Ballistic Accumulator model. ISR was best accounted for as a change in the accumulation rate. We suggest this parameter represents the overall desirability of a particular course of action, the evidence for which may be derived from a variety of sensory and non-sensory sources.     

'Reverberation time', dreaming and the capacity to dream

In this paper the author suggests that understanding the roots of the subjective sense of time can throw light on the disturbances in psychic time which are found in particular in the more severe pathologies. She introduces the argument that the roots of the development of the sense of time rest on a primitive sense of time she calls 'reverberation time'. By this notion she refers to the particular quality of the earliest 'back and forth' internalized exchange with the mother in which the auditory dimension plays a significant part. Referring to a wide range of literature and clinical examples, the author thus suggests that the subjective sense of time is created by the reverberation between mother and infant. Disturbances in this area will be reflected in the pathological 'arresting' of time which is observed in the different pathologies and, in particular, around the negotiation of the depressive position and the oedipal situation. Extending this argument, the author goes on to suggest that it is the internalization of this experience of 'reverberation' which lies at the heart of the experience of dreaming; she considers that dreaming understood as an internal dialogue points both to its roots in the relationship to the maternal object and to its fundamental role in psychic life. The author concludes that 'reverberation time' is also the building block of a psychoanalysis, leading to 'unfreezing' psychic time and enabling the reconnection of 'here and now' with 'there and then' in a flexible way which promotes open possibilities, and that this takes place via the analyst's reverie, or time of reverberation.     

ENSEMBLE RECORDINGS IN AWAKE RATS: ACHIEVING BEHAVIORAL REGULARITY DURING MULTIMODAL STIMULUS PROCESSING AND DISCRIMINATIVE LEARNING

To meet an increasing need to examine the neurophysiological underpinnings of behavior in rats, we developed a behavioral system for studying sensory processing, attention and discrimination learning in rats while recording firing patterns of neurons in one or more brain areas of interest. Because neuronal activity is sensitive to variations in behavior which may confound the identification of neural correlates, a specific aim of the study was to allow rats to sample sensory stimuli under conditions of strong behavioral regularity. Our behavioral system allows multimodal stimulus presentation and is coupled to modules for delivering reinforcement, simultaneous monitoring of behavior and recording of ensembles of well isolated single neurons. Using training protocols for simple and compound discrimination, we validated the behavioral system with a group of 4 rats. Within these tasks, a majority of medial prefrontal neurons showed significant firing‐rate changes correlated to one or more trial events that could not be explained from significant variation in head position. Thus, ensemble recordings can be combined with discriminative learning tasks under conditions of strong behavioral regularity.     

LEARNING TO TIME: A PERSPECTIVE

In the last decades, researchers have proposed a large number of theoretical models of timing. These models make different assumptions concerning how animals learn to time events and how such learning is represented in memory. However, few studies have examined these different assumptions either empirically or conceptually. For knowledge to accumulate, variation in theoretical models must be accompanied by selection of models and model ideas. To that end, we review two timing models, Scalar Expectancy Theory (SET), the dominant model in the field, and the Learning‐to‐Time (LeT) model, one of the few models dealing explicitly with learning. In the first part of this article, we describe how each model works in prototypical concurrent and retrospective timing tasks, identify their structural similarities, and classify their differences concerning temporal learning and memory. In the second part, we review a series of studies that examined these differences and conclude that both the memory structure postulated by SET and the state dynamics postulated by LeT are probably incorrect. In the third part, we propose a hybrid model that may improve on its parents. The hybrid model accounts for the typical findings in fixed‐interval schedules, the peak procedure, mixed fixed interval schedules, simple and double temporal bisection, and temporal generalization tasks. In the fourth and last part, we identify seven challenges that any timing model must meet.     

Attentional processing of location and color cues during driving

Studies have shown that prior information concerning the spatial location of a subsequent target facilitates the selection of that target for further visual processing in three-dimensional (3-D) space. Using Posner's cuing paradigm, our work examined the reaction time of drivers when cue duration and peripheral environment luminance was changed, and explored the effect color and location on reaction time. Experiment 1 showed that reaction time was not affected by cue duration, and that shifts of attention operated more efficiently for cue location validity. Experiment 2 showed that there was no main effect of background luminance on reaction time. Experiment 3 showed that location produces a greater effect than color.     

Visual discrimination of vowel duration

Discrimination of vowel duration was explored with regard to discrimination threshold, error bias, and effects of modality and consonant context. A total of 122 normal-hearing participants were presented with disyllabic-like items such as /lal-lal/ or /mam-mam/ in which the lengths of the vowels were systematically varied and were asked to judge whether the first or second vowel was longer. Presentation was either visual, auditory, or audiovisual. Vowel duration differences varied in 24 steps: 12 with a longer first /a/ and 12 with a longer last /a/ (range: ±33–400 ms). Results: 50% JNDs were smaller than the lowest tested step size (33 ms); 75% JNDs were in the 33–66 ms range for all conditions but V /lal/, with a 75% JND at 66–100 ms. Errors were greatest for visual presentation and for /lal-lal/ tokens. There was an error bias towards reporting the first vowel as longer, and this was strongest for /mam-mam/ and when both vowels were short, possibly reflecting a sublinguistic processing strategy.     

The global non-entropic arrow of time: from global geometrical asymmetry to local energy flow

Since the nineteenth century, the problem of the arrow of time has been traditionally analyzed in terms of entropy by relating the direction past-to-future to the gradient of the entropy function of the universe. In this paper, we reject this traditional perspective and argue for a global and non-entropic approach to the problem, according to which the arrow of time can be defined in terms of the geometrical properties of spacetime. In particular, we show how the global non-entropic arrow can be transferred to the local level, where it takes the form of a non-spacelike local energy flow that provides the criterion for breaking the symmetry resulting from time-reversal invariant local laws.     

Visual and tactile action effects determine bimanual coordination performance

Effect-based models of motor control assign a crucial role to anticipated perceptual feedback in action planning. Two experiments were conducted to test the validity of this proposal for discrete bimanual key press responses. The results revealed that the normally observed performance advantage for the preparation of two responses with homologous rather than non-homologous fingers becomes inverted when homologous fingers produce non-identical visual effects, and non-homologous fingers produce identical visual effects. In the second experiment the finger homology effect was strongly reduced when homologous fingers produced non-identical tactile feedback. The results show that representations of to-be-produced visual and tactile action effects both contribute to action planning, though possibly to a varying degree. Implications of these results for effect-based models of motor control are considered.