Using adaptive psychophysics to identify the neural network reset time in subsecond interval timing

State-dependent network models of sub-second interval timing propose that duration is encoded in states of neuronal populations that need to reset prior to a novel timing operation to maintain optimal timing performance. Previous research has shown that the approximate boundary of this reset interval can be inferred by varying the inter-stimulus interval between two to-be-timed intervals. However, the estimated boundary of this reset interval is broad (250–500 ms) and remains under-specified with implications for the characteristics of state-dependent network dynamics sub-serving interval timing. Here, we probed the interval specificity of this reset boundary by manipulating the inter-stimulus interval between standard and comparison intervals in two sub-second auditory duration discrimination tasks (100 and 200 ms) and a control (pitch) discrimination task using adaptive psychophysics. We found that discrimination thresholds improved with the introduction of a 333 ms inter-stimulus interval relative to a 250 ms inter-stimulus interval in both duration discrimination tasks, but not in the control task. This effect corroborates previous findings of a breakpoint in the discrimination performance for sub-second stimulus interval pairs as a function of an incremental inter-stimulus delay but more precisely localizes the minimal inter-stimulus delay range. These results suggest that state-dependent networks sub-serving sub-second timing require approximately 250–333 ms for the network to reset to maintain optimal interval timing.

Temporal Factors Modulate Haloperidol-Induced Conditioned Catalepsy

Repeated pairings of a neutral context and the effects of haloperidol give rise to conditioned catalepsy when the context is subsequently presented in a drug-free test. In order to confirm whether this response is based on Pavlovian processes, we conducted two experiments involving two manipulations that affect conditioning intensity in classical conditioning procedures: time of joint exposure to the conditioned and the unconditioned stimulus, and the length of the inter-stimulus interval (ISI). The results revealed that both an increase in the length of context-drug pairings during conditioning and a reduced ISI between drug administration and context exposure increased conditioned catalepsy. These results are discussed in terms of the temporal peculiarities of those procedures that involve drugs as the unconditioned stimulus along with the role of Pavlovian conditioning in context-dependent catalepsy.

Location-independent feature binding in visual working memory for sequentially presented objects

Spatial location is believed to have a privileged role in binding features held in visual working memory. Supporting this view, Pertzov and Husain (Attention, Perception, & Psychophysics, 76(7), 1914–1924, 2014) reported that recall of bindings between visual features was selectively impaired when items were presented sequentially at the same location compared to sequentially at different locations. We replicated their experiment, but additionally tested whether the observed impairment could be explained by perceptual interference during encoding. Participants viewed four oriented bars in highly discriminable colors presented sequentially either at the same or different locations, and after a brief delay were cued with one color to reproduce the associated orientation. When we used the same timing as the original study, we reproduced its key finding of impaired binding memory in the same-location condition. Critically, however, this effect was significantly modulated by the duration of the inter-stimulus interval, and disappeared if memoranda were presented with longer delays between them. In a second experiment, we tested whether the effect generalized to other visual features, namely reporting of colors cued by stimulus shape. While we found performance deficits in the same-location condition, these did not selectively affect binding memory. We argue that the observed effects are best explained by encoding interference, and that memory for feature binding is not necessarily impaired when memoranda share the same location.

The effects of letter matrix and inter stimulus interval on P300 Event Related Potential

According to the General Statistics Office (Ministry of Planning and investment) collaborated with the United Nations Children’s Fund in Viet Nam, from 2016 to 2017, there were nearly 5 million households which had disabilities in the country. The proportion of people with disabilities who were over 2 years old accounted for 7% of the population. Another statistic is based on the Christopher & Dana Reeve Foundation report in 2013, about 5.4 million Americans suffer from disability [2]. Many research works, therefore, have been built with the aim of improving the ability of movement and communication, based on biomedical signals, especially the Brain-Computer Interface (BCI) system. BCI is a technology that enables the use of the brain’s neural activity to communicate with others or to control machines, artificial limbs, or robots without direct physical movements. BCI based on electroencephalogram (EEG) can be applied to the disabled individual system. In recent years, there are many people suffering from the loss of all voluntary muscle control in Viet Nam. Therefore, they really need alternative interaction methods to control their behaviors with external environment. Thanks to the development of Brain-Computer interfaces and the EEG headset have been helping people who are incapable of any motion for function can communicate with the external world, due to the P300 signal. As the important consideration to discover which factors affect the accuracy of BCI system to improve communication quality for the ability of disabled people, we decide to discover the impact of character matrix size and inter stimulus interval on event related potential. The duration of the inter stimulus interval (ISI) between targets is set at 187,5 ms and 125 ms for two different matrix sizes 3x3 and 6x6. The results provide that the largest amplitudes of P300 waveforms occur remarkably at the occipital and frontal channels and are higher than in 6x6 letter matrix compared with 3x3 matrix. The different matrix size and ISI does not affect on the appearance time of the P300 signal, and it is in the range 235-244 ms after stimulation. These good results promise to help other researches to build a perfect experimental procedure in real assistance application for using BCI – P300 systems.

Tapping Behavior and Inter-Stimulus Interval in Isochronous Sound Sequence

The main objective of this study is to examine anticipatory tapping and reactive tapping under two different inter-stimulus interval (ISI). Healthy participants (N = 30) aged from 18 to 35 years voluntarily participated in the study. The results show that the ISI plays an important role in sensory motor synchronization (SMS). The analysis of asynchrony revealed that two different type of tapping occurred under two different ISI. Under short ISI (1000 ms), participants executed their responses before the tone (i.e., anticipatory tapping driven by feed-forward motor control). Under long ISI (2000 ms), participants executed their responses after the tone (i.e., reactive tapping driven by feed-back motor control mechanism). In summary, participants showed anticipatory tapping in the absence of top-down attention and reactive tapping with the involvement of top-down attention.