Into the Mind’s Eye: Exploring the Fast-Same Effect in the Same-Different Task

Though the voluntary task-switching paradigm asks participants to select their task and whether to switch on each trial internally, external bottom-up information from the stimulus affects task choice, such that participants were more likely to switch tasks on stimulus switches than stimulus repetitions (e.g., Mayr & Bell, Psychological Science, 17(9), 774-780, 2006). In previous research, both the perceptual elements and the identity of the stimulus changed on a stimulus switch, producing ambiguity with regard to which of the two changes drove the effect. By intermixing two stimulus types (words and Arabic numerals in Experiment 1; words and dot arrays in Experiment 2), we aimed to disentangle whether stimulus or identity repetitions drive stimulus-based switching. We produced lists with equal numbers of full stimulus repetitions (4 → 4), full stimulus switches (4 → one), and trials where the identity repeated but the stimulus changed (identity repetitions; 4 → four). We replicated the previous finding that participants were more likely to repeat the previous task on a full stimulus repetition than they were with a full stimulus switch. However, identity repetitions were not statistically different from full stimulus switches. These findings indicate that bottom-up perceptual information, rather than stimulus identity, may be what drives stimulus-based switching.

Encoding/retrieval dissociation in working memory for human body forms

Event Abstract Back to Event Timing precision in population coding of natural scenes in the early visual system The precision of neuronal spike trains is at the center of a fundamental debate in neuroscience as to what aspects of neuronal signaling are important in representing information in the brain. Individual neurons can have extremely precise and repeatable responses to the visual stimuli that strongly drive them (down to 1-ms variability), but they exhibit seemingly degraded temporal precision in response to suboptimal stimuli. In the presence of natural scenes, the activity of individual neurons is precisely timed across repeated presentations of the visual stimulus, even though natural stimuli tend to vary on a time scale that is several times slower. However, in most natural circumstances, the brain does not have access to multiple repetitions of the same identical stimulus, and, therefore, it is the precision of spiking across neuronal sub-populations on single trials that is ethologically relevant. While synchrony across neurons in the retina and visual cortex has been reported at various time scales, which can depend on the visual stimulus, the temporal precision of the neural code directly entering primary visual cortex, and its dependence on the stimulus, are still unknown. In this study (Desbordes et al., PLoS Biology, in press), we used natural visual stimuli to investigate spike timing precision in populations of geniculate neurons that serve as the direct input to visual cortex. A short movie of a natural scene recorded from a “cat-cam” (Kayser et al., 2003) was presented repeatedly to anesthetized cats while recording extracellular activity of multiple single units in the lateral geniculate nucleus (LGN) in vivo. To test how spike timing precision was affected by the properties of the visual stimulus, the same movie was presented both at high contrast and at low contrast. The absolute timing of firing events (or groups of closely spaced spikes) changed from trial to trial, and more so at low contrast than at high contrast, indicating that the response of individual neurons is less precise across stimulus repetitions when contrast is reduced. However, the relative timing of spikes occurring in the same trial was insensitive to changes in stimulus contrast - not only within cells but also across neighboring cells. At the population level, spike timing precision across LGN cells remained on the order of ~10 ms, irrespective of contrast. While it is well known that the response properties of single cells are strongly modulated by contrast adaptation, which has effects including slower temporal dynamics and increased gain and selectivity at lower contrast, our results indicate that the temporal precision of the LGN population code is globally maintained in the face of a reduction in contrast. Since closely timed spikes are more likely to induce a spike in the downstream cortical neuron to which they are projecting (Alonso et al., Nature, 1996), and since fine temporal precision is necessary in representing the more slowly varying natural environment (Butts et al., Nature, 2007), preserving the relative timing of spikes at a resolution of ~10 ms may be a crucial aspect of the neural code entering primary visual cortex. Conference: Computational and systems neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: (2009). Timing precision in population coding of natural scenes in the early visual system. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.325 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Feb 2009; Published Online: 04 Feb 2009. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Google Google Scholar PubMed Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

In the working memory model, phonological and visuospatial information are stored by separate and independent systems. However, sometimes binding of visual and verbal information must occur. This study investigated whether these memory systems cooperate in the recall of spatial location of a stimulus defined by both types of information. Participants memorized the spatial locations in which name-and-face pairs were presented and either recalled the position of a test stimulus in which the two types of information were always present (Experiment 1) or recalled the position of a test stimulus that non-predictively contained either the visual or verbal information (Experiment 2). The results showed no cooperation between visuospatial and phonological systems when both types of information were present in the test stimulus. Rather, a clear preference for verbal information was found (Experiment 1). When the test stimulus contained only one type of information, recall based on both verbal and visual information was impaired (Experiment 2). These results suggest that visual and verbal information are not automatically integrated into memory and that storage capacity is smaller for integrated information than for isolated information.

Participants tend to match identical pairs of stimuli faster than different pairs. Despite many endeavours to explain this fast-same effect, there is still no theoretical consensus. A potential reason for the lack of consensus is that the cognitive architecture and capacity underlying such phenomenon is assumed and not formally tested. For example, the dual-process approach suggests that Same responses arise from a parallel treatment, whereas Different responses arise from a serial treatment. It also suggests that in both conditions, the capacity of the process is unaffected by workload (unlimited capacity). Alternative approaches argue that the fast-same effect can be explained by parallel or coactive architectures with channels working in either limited or super capacity. In this study, we formally assess the architecture (three possibilities: serial, parallel and coactive) and the capacity (three possibilities: unlimited, limited and super-capacity) of the cognitive system in a Same-Different task using Systems Factorial Technology (SFT). We recruited twenty participants to perform a double-factorial task lasting four sessions. Because of the lack of effectiveness of the blurring manipulation, we cannot draw a strong conclusion about the cognitive architecture. As for the capacity, the results show that it is mostly limited for the majority of participants. However, between 300 and 500 ms, participants tend to have a much stronger processing capacity in the Same condition compared to the Different condition. This short but strong burst of activity for identical stimuli might explain the fast-same effect.

Habituation and sensitization are important behavioural responses to repeated exposure of painful stimuli. Whereas within-session response dynamics to nociceptive stimuli is well characterized, little is known about long-term behaviour due to repetitive nociceptive stimulation. We used a standardized longitudinal heat pain paradigm in 66 healthy participants, 21 patients with chronic low back pain and 22 patients with depression who received daily sessions of 60 suprathreshold heat stimuli (48 °C each) for eight consecutive days. All three groups showed the same response: Repeated painful stimulation over several days resulted in substantially decreased pain ratings to identical painful stimuli. The decreased perception of pain over time was associated with a very robust increase in pain ratings in each single pain session, i.e., all participants sensitized within sessions and habituated between sessions. This uniform pattern was equally present in all examined groups. Chronic pain and depression do not seem to interfere with short-term sensitization and long-term habituation in this model of repetitive phasic heat pain.

Event-related potentials were recorded in response to intermittently presented, non-attended trains of identical auditory stimuli in healthy 9-year-old children. In abnormally distractible children (n =24), the first tone in each train elicited a significantly larger N1 vertex response than in the non-distractible children (n 24), suggesting that increased distractibility may be associated with an abnormally strong cerebral orienting towards non-attended stimuli. A later negativity at around 300 ms, which increases in amplitude with stimulus repetition and may thus reflect the building up of a functional neuronal representation of the stimulus properties, was significantly smaller in the distractible than in the non-distractible children. These findings demonstrate that event-related potential measures may be useful in helping to understand the information processing found in distractible children.

Neuroplasticity in the acoustic startle reflex in larval zebrafish

Repetition of identical face stimuli leads to fMRI response attenuation (fMRI adaptation, fMRIa) in the core face-selective occipito-temporal visual cortical network, involving the bilateral fusiform face area (FFA) and the occipital face area (OFA). However, the functional relevance of fMRIa observed in these regions is unclear as of today. Therefore, here we aimed at investigating the relationship between fMRIa and face perception ability by measuring in the same human participants both the repetition-induced reduction of fMRI responses and identity discrimination performance outside the scanner for upright and inverted face stimuli. In the correlation analysis, the behavioral and fMRI results for the inverted faces were used as covariates to control for the individual differences in overall object perception ability and basic visual feature adaptation processes, respectively. The results revealed a significant positive correlation between the participants' identity discrimination performance and the strength of fMRIa in the core face processing network, but not in the extrastriate body area (EBA). Furthermore, we found a strong correlation of the fMRIa between OFA and FFA and also between OFA and EBA, but not between FFA and EBA. These findings suggest that there is a face-selective component of the repetition-induced reduction of fMRI responses within the core face processing network, which reflects functionally relevant adaptation processes involved in face identity perception.

The capacity to suppress irrelevant incoming input, termed sensory gating, is one of the most investigated inhibitory processes associated with cognitive impairments due to aging. The aim of this study was to examine the influence of aging on sensory gating by using somatosensory event-related potentials (ERPs) elicited by repetitive non-painful tactile stimulation (paired-pulsed task). Somatosensory ERPs were recorded in 20 healthy young adults and 20 healthy older adults while they received two identical pneumatic stimuli (S1 and S2) of 100 ms duration with an inter-stimulus interval of 550 ± 50 ms on both forefingers. The difference between the somatosensory ERPs amplitude elicited by S1 and S2 was computed as a sensory gating measure. The amplitude and the latency of P50, N100 and late positive complex (LPC) were analyzed as well as the source generators of the gating effect. Reduced sensory gating was found in older individuals for N100 at frontal and centro-parietal electrodes and for LPC at fronto-central electrodes. Source localization analyses also revealed a reduced current density during gating effect in the older group in frontal areas in N100 and LPC. Moreover, older individuals showed delayed latencies in N100. No significant gating effect differences were found between groups in P50. These findings suggest an age-related slowing of processing speed and a reduced efficiency of inhibitory mechanisms in response to repetitive somatosensory information during stimulus evaluation, and a preservation of processing speed and inhibitory control during early stimulus coding in aging.

Based on recent findings regarding the mechanical determinants of sprint performance, resisted sled sprint (RSS) training may provide an effective tool for the improvement of sprint acceleration and maximal velocity. However, the volume and intensity for effective RSS training in different populations is unclear. The primary objective was to evaluate the effectiveness of RSS training compared with unresisted sprint (URS) training, and the differential effects of sled load on RSS training outcomes. STUDY ELIGIBILITY AND APPRAISAL: A systematic review was performed primarily using PubMed and SPORTDiscus databases. Peer-reviewed studies were accepted only if the participants used a sled towing device for a longitudinal intervention of resisted sprint training, and if RSS training was the primary difference in training intervention between groups. Effect size (ES) reported using Cohen's d was presented to compare the magnitude of effect between both dependent and independent groups. A total of 11 studies fulfilled the eligibility criteria. Sled loads were prescribed either as a percentage of body mass (%BM), a targeted reduction in velocity compared with unresisted sprint velocity (%V(dec)) or as an absolute load (kg). RSS training with 'light' (<10 %BM or <10 %V(dec)) loads provide 'small' decrements in acceleration (-1.5%, ES = 0.50) to 'moderate' improvements in maximal sprint velocity (2.4%, ES = 0.80) in sprint-trained individuals. 'Moderate' (10-19.9%BM or 10-14.9%V(dec)) to 'very heavy' (>30%BM or >30%V(dec)) sled loads provide 'trivial' to 'extremely large' improvements in acceleration performance (0.5-9.1%, ES = 0.14-4.00) in strength-trained or team sport individuals. Whether RSS training is more effective than URS training in the improvement of acceleration or maximal sprint velocity remains equivocal. RSS training is a novel training method with potential for the improvement of sprint performance, but its performance benefits over URS training remain to be conclusively demonstrated. Between-study comparisons are limited primarily by discrepancies in the training status and phase of the participants, and sled load prescription. Future work is required to define the optimal load and volume for RSS depending on the specific components of sprint performance to be enhanced.

Most fatigue-loading research has concentrated on constant-amplitude tests, which seldom represent actual service conditions. Because of the significant time and expense associated with variable-amplitude experiments, researchers often employ block/step-loading tests to evaluate the effects of variable-amplitude loading. These tests utilize various sequences of low-to-high and high-to-low loads to simulate real-world scenarios. Empirical investigations have shown inconsistencies in the damage accumulation under different load sequences. Although literature reviews exist for simulation and experimental methods, there is limited research examining the impact of step/variable-amplitude loading on adhesive joints in composite materials. This review aims to address this gap by comprehensively analyzing the effects of load sequence and block loading on fatigue damage progression in fiber-reinforced polymer composites. Additionally, the applicability of various step-loading fatigue damage accumulation models to adhesive materials is evaluated through numerical simulation to study its suitability in predicting fatigue failure. This review also explores recent theoretical advancements in this field over the past few years, examining more than 100 fatigue damage accumulation models categorized into seven subcategories: (i) linear damage rules, (ii) nonlinear damage curve and two-stage linearization models, (iii) life curve modification models, (iv) models based on crack growth concepts, (v) continuum damage mechanics-based models, (vi) material degradation models, and (vii) energy-based models. Finally, numerical simulations using the most common nonlinear cumulative fatigue damage accumulation models were conducted to predict fatigue failure in adhesively bonded joints under four step-loading tests, and the results were compared with the experimental data. Numerical simulations revealed the need and scope of further development of a fatigue failure model under step/variable loading. This comprehensive review offers valuable insights into the complex nature of fatigue failure in adhesive joints under variable loading conditions and highlights current state-of-the-art nonlinear fatigue damage accumulation models for adhesive materials.

Participants are biased in responding to stimuli associated with themselves compared with stimuli related to other people. This self-bias may reflect the reward value of self-related stimuli (Sui, He, & Humphreys, 2012). In this article, we examined the identification of self- and reward-associated stimuli under conditions in which either single or redundant stimuli were presented. The redundant stimuli could be the same shape or they could be different shapes both associated with either the self or a friend or high or low reward. We formally tested whether the redundant stimuli violated the independent race model for the identification of multiple stimuli (Miller, 1982) and whether the redundant stimuli were processed with super- or limited-capacity (Townsend & Eidels, 2011). We found that redundant self stimuli alone both violated the independent race model and were processed with super-capacity. In contrast, the redundant high reward stimuli did not show race inequality and were associated with limited capacity processing. The data advance our theoretical understanding of self bias both by demonstrating that it can be distinguished from effects of reward, and by suggesting that self-bias can result from the enhanced integration of stimuli associated with the self. The implications for understanding self bias effects are discussed.

The inhibitory deficit hypothesis of cognitive aging posits that older adults’ inability to adequately suppress processing of irrelevant information is a major source of cognitive decline. Prior research has demonstrated that in response to task-irrelevant auditory stimuli there is an age-associated increase in the amplitude of the N1 wave, an ERP marker of early perceptual processing. Here, we tested predictions derived from the inhibitory deficit hypothesis that the age-related increase in N1 would be 1) observed under an auditory-ignore, but not auditory-attend condition, 2) attenuated in individuals with high executive capacity (EC), and 3) augmented by increasing cognitive load of the primary visual task. ERPs were measured in 114 well-matched young, middle-aged, young-old, and old-old adults, designated as having high or average EC based on neuropsychological testing. Under the auditory-ignore (visual-attend) task, participants ignored auditory stimuli and responded to rare target letters under low and high load. Under the auditory-attend task, participants ignored visual stimuli and responded to rare target tones. Results confirmed an age-associated increase in N1 amplitude to auditory stimuli under the auditory-ignore but not auditory-attend task. Contrary to predictions, EC did not modulate the N1 response. The load effect was the opposite of expectation: the N1 to task-irrelevant auditory events was smaller under high load. Finally, older adults did not simply fail to suppress the N1 to auditory stimuli in the task-irrelevant modality; they generated a larger response than to identical stimuli in the task-relevant modality. In summary, several of the study’s findings do not fit the inhibitory-deficit hypothesis of cognitive aging, which may need to be refined or supplemented by alternative accounts.

A new high frequency magnetic stimulator, Labmag, is described which may be used in clinical neurophysiology and for the treatment of spasticity in multiple sclerosis. In order to avoid heating of the coil during repetitive stimulation, an oil/air cooling system was employed. The magnetic stimulus waveform is a half cosine with a rise time of 200 microseconds and a pulse width of 400 microseconds induced by alternating capacitor voltage. The Labmag product was compared with a commercially available high frequency stimulator, MagPro. The electric fields induced by Labmag were half the size of those induced by MagPro at identical stimulus intensities. Using a leaky integrator to simulate the effects on neurons, only minor differences in integrated electric fields were observed. There were no changes of the electric fields in relation to coil geometry. A minor difference in electric fields (1.0 +/- 0.8%) was observed when the polarity of the capacitor voltage alternated. Compound muscle action potentials (CMAPs) evoked by transcranial magnetic stimulation were recorded from the first dorsal interosseous muscle (FDI) in eight subjects. Threshold intensities of CMAPs evoked by Labmag (58 +/- 7%) were significantly smaller (p < 0.05) than threshold intensities obtained with MagPro (63 +/- 8%). Peak-to-peak amplitudes, P-Pamps, of CMAPs were significantly smaller after single stimulations with Labmag at stimulation intensities of 130 and 140% of threshold intensity.