Repeat Trials Research Articles

A carry-over task rule in task switching: An ERP investigation using a Go/Nogo paradigm

Investigations of executive control using a task-switching paradigm have consistently found longer reaction times for task-switch trials than task-repetition trials. This switch cost may result from interference by a stimulus-response (SR) rule carried over from the preceding alternative task. We examined event-related brain potential (ERP) evidence for such carry-over effects using a combined paradigm of task switching with Go/Nogo; Nogo trials, which require no response execution, should expose carry-over effects from preceding trials. On Go trials, twelve participants performed a button-pressing task in compatible (hand and signal direction consistent) and incompatible conditions, which switched predictably every three trials. Reaction times were longer on switch than on repetition trials. On compatible switch trials, a stimulus-locked lateralized readiness potential (sLRP) for Nogo stimuli revealed a positive dip, suggesting incorrect response activation in the early automatic process that was induced by a SR rule carried over from the preceding task.

The Effects of Foreknowledge and Task-Set Shifting as Mirrored in Cue- and Target-Locked Event-Related Potentials

The present study examined the use of foreknowledge in a task-cueing protocol while manipulating sensory updating and executive control in both, informatively and non-informatively pre-cued trials. Foreknowledge, sensory updating (cue switch effects) and task-switching were orthogonally manipulated in order to address the question of whether, and to which extent, the sensory processing of cue changes can partly or totally explain the final task switch costs. Participants responded faster when they could prepare for the upcoming task and if no task-set updating was necessary. Sensory cue switches influenced cue-locked ERPs only when they contained conceptual information about the upcoming task: frontal P2 amplitudes were modulated by task-relevant cue changes, mid-parietal P3 amplitudes by the anticipatory updating of stimulus-response mappings, and P3 peak latencies were modulated by task switching. Task preparation was advantageous for efficient stimulus-response re-mapping at target-onset as mirrored in target N2 amplitudes. However, N2 peak latencies indicate that this process is faster for all repeat trials. The results provide evidence to support a very fast detection of task-relevance in sensory (cue) changes and argue against the view of task repetition benefits as secondary to purely perceptual repetition priming. Advanced preparation may have a stronger influence on behavioral performance and target-locked brain activity than the local effect of repeating or switching the task-set in the current trial.

Bénéfices et risques néonataux de la tentative de voie basse comparée à la césarienne programmée en cas d’antécédent de césarienne

To evaluate neonatal outcome after elective repeat cesarean delivery (ERCD) versus trial of labor (TOL) after previous cesarean delivery. This systematic evidence review is based on Pubmed search, Cochrane library and experts recommendations. The risks of fetal, perinatal and neonatal mortality are low after previous cesarean delivery but significantly higher for TOL as compared with ERCD. The risk of bag-and-mask ventilation and intubation for meconium-stained amniotic fluid are higher for TOL as compared with ERCD. Infants born after ERCD are more likely presented transient tachypnea. The risk of hypoxic encephalopathy/asphyxia is low after previous cesarean delivery but significantly higher for TOL as compared with ERCD. The risk of neonatal sepsis after previous cesarean delivery is significantly higher for TOL as compared with ERCD. There is no significant difference between TOL or ERCD regarding NICU admission. The strength of evidence is low to conclude about the impact of route of delivery upon birth trauma and Apgar score. The risk of the main neonatal complications is low whatever the route of delivery after previous caesarean delivery. However, the risk of perinatal mortality, bag-and-mask ventilation, perinatal asphyxia, is higher after TOL compared with ERCD. The risk of transient tachypnea is higher after ERCD compared with TOL.

Target localization among concurrent sound sources: No evidence for the inhibition of previous distractor responses

The visuospatial negative priming effect-that is, the slowed-down responding to a previously ignored location-is partly due to response inhibition associated with the previously ignored location (Buckolz, Goldfarb, & Khan, Perception & Psychophysics 66:837-845 2004). We tested whether response inhibition underlies spatial negative priming in the auditory modality as well. Eighty participants localized a target sound while ignoring a simultaneous distractor sound at another location. Eight possible sound locations were arranged in a semicircle around the participant. Pairs of adjacent locations were associated with the same response. On ignored repetition trials, the probe target sound was played from the same location as the previously ignored prime sound. On response control trials, prime distractor and probe target were played from different locations but were associated with the same response. On control trials, prime distractor and probe target shared neither location nor response. A response inhibition account predicts slowed-down responding when the response associated with the prime distractor has to be executed in the probe. There was no evidence of response inhibition in audition. Instead, the negative priming effect depended on whether the sound at the repeatedly occupied location changed identity between prime and probe. The latter result replicates earlier findings and supports the feature mismatching hypothesis, while the former is compatible with the assumption that response inhibition is irrelevant in auditory spatial attention.

Inhibited prime-trial distractor responses solely produce the visual spatial negative priming effect

Responding to a target's current (probe trial) location is slower when it appears at a former distractor-occupied position (i.e., ignored-repetition [IR] trial), relative to when it arises at a new location (i.e., control trial). This RT(IR) > RT(Control) inequality defines the spatial negative priming (SNP) effect in latency terms. It is uncertain whether the elevated RT(IR) is due to the inhibition of the distractor-occupied location or to the inhibition of this location's assigned manual response (SNP locus issue). The main aim here was to examine the SNP locus issue. Notably, our SNP design used centrally presented visual events and included having two locations share a common response (many:1 location-to-response mapping) and the use of informative (70% validity) or uninformative probe-trial response cues. The many:1 mapping trials allowed for the detection of location and response inhibition presence. Results showed that the latter, but not the former, causes inhibitory aftereffects (e.g., SNP) following uninformative response cues. Consistent with this finding, when the informative response cue was valid and was assigned to the many:1 probe response that had just served as the prime distractor response, inhibitory aftereffects were eliminated, when the probe target appeared at the prime distractor position (IR trial) or at a new location (distractor-response repeat trial). Blocked retrieval of stored distractor-processing representations was proposed as the mechanism for inhibitory aftereffect prevention.

Mechanisms of change: Effects of repetitive exposure to feared stimuli on the brain's fear network

Repetitive exposure to feared stimuli is considered as the essential element in therapy with phobic patients. However, the mechanisms mediating symptom reduction and their underlying neurobiological processes are poorly understood. Therefore, we presented the same fear-relevant and neutral stimuli repeatedly to individuals with high and low fear of animals during fMRI scanning. High-, but not low-fearful individuals showed an initial fear-stimulus-related potentiation of amygdala and insula activity. Potentiation of the amygdala in the high-fearful group habituated quickly, but insula activity was still potentiated during later repetition trials. Both groups showed an initial potentiation of the dorsomedial prefrontal cortex (dmPFC) that continuously decreased in low-, but not in high-fearful participants. Thus, within-session habituation may occur on an automatic processing level (amygdala), but does not cause lasting neural changes on a higher order cortical level (dmPFC).

Neural Mechanisms Underlying the Cost of Task Switching: An ERP Study

BackgroundWhen switching from one task to a new one, reaction times are prolonged. This phenomenon is called switch cost (SC). Researchers have recently used several kinds of task-switching paradigms to uncover neural mechanisms underlying the SC. Task-set reconfiguration and passive dissipation of a previously relevant task-set have been reported to contribute to the cost of task switching.Methodology/Principal FindingsAn unpredictable cued task-switching paradigm was used, during which subjects were instructed to switch between a color and an orientation discrimination task. Electroencephalography (EEG) and behavioral measures were recorded in 14 subjects. Response-stimulus interval (RSI) and cue-stimulus interval (CSI) were manipulated with short and long intervals, respectively. Switch trials delayed reaction times (RTs) and increased error rates compared with repeat trials. The SC of RTs was smaller in the long CSI condition. For cue-locked waveforms, switch trials generated a larger parietal positive event-related potential (ERP), and a larger slow parietal positivity compared with repeat trials in the short and long CSI condition. Neural SC of cue-related ERP positivity was smaller in the long RSI condition. For stimulus-locked waveforms, a larger switch-related central negative ERP component was observed, and the neural SC of the ERP negativity was smaller in the long CSI. Results of standardized low resolution electromagnetic tomography (sLORETA) for both ERP positivity and negativity showed that switch trials evoked larger activation than repeat trials in dorsolateral prefrontal cortex (DLPFC) and posterior parietal cortex (PPC).Conclusions/SignificanceThe results provide evidence that both RSI and CSI modulate the neural activities in the process of task-switching, but that these have a differential role during task-set reconfiguration and passive dissipation of a previously relevant task-set.

Physical Layer Authentication over MIMO Fading Wiretap Channels

In a wide band and multipath rich environment, precise channel estimation allows authenticating the source and protecting the integrity of a message at the physical layer without the need of a pre-shared secret key. This allows also a reduction of the burden on the authentication protocols at higher layers. In this paper we develop an authentication scheme in the framework of hypothesis testing that suits a multiple wiretap channels environment with correlated fading, as is the case of multiple input multiple output (MIMO) systems and/or orthogonal frequency division multiplexing (OFDM) modulation. By allowing some degree of correlation among the channels, we formulate the optimal attack strategy for the cases of both single attempt and multiple repeated trials. For the latter scenario, due to the complexity of the optimal solution, we also develop a simpler suboptimal attack strategy. The performance of the proposed methods is evaluated in a MIMO/OFDM scenario and numerical results show the merits of the proposed approaches that can be adopted as a layer one authentication mechanism.

Can an Accelerometer-Based Monitor be used to Accurately Assess Physical Activity in a Population of Survivors of Critical Illness?

Purpose:To investigate the validity and reliability of the Activity Monitoring Pod (AMP331) to record gait parameters in healthy young adults (YA) and intensive care unit inpatients (ICU).Methods:YA (N=15) completed a series of over-ground walks. Another 15 YA completed a series of treadmill walks. The ICU group (N=20) completed a series of over-ground walks with repeat trials. Gait parameters were recorded simultaneously by the AMP 331 and the Vicon (YA) and the AMP 331, direct observation and a stopwatch (ICU).Results:For the YA over-ground, no significant differences were found between the measures recorded by the systems. For the YA treadmill, 43% of the measures differed (P < .05). For the ICU group, the AMP331 underestimated distance and speed by 3m and 25cm/s respectively. Reliability measures (ICU group) for distance (ICC 0.99, 95%CI 0.98 – 0.99) and step count (ICC 0.99, 95%CI 0.99 – 1.00) were excellent.Conclusions:The AMP 331 is a valid instrument for recording basic gait parameters for over-ground walking in healthy YA and ICU survivors.

Consciousness Studies and a Transformation of the Western Worldview

The emerging field of consciousness studies offers the perspective we need to make our global human community sustainable.

Elective repeat cesarean delivery compared with spontaneous trial of labor after a prior cesarean delivery: a propensity score analysis

The purpose of this study was to determine outcomes, after the use of propensity score techniques, to create balanced groups according to whether a woman undergoes elective repeat cesarean delivery (ERCD) or trial of labor (TOL). Women who were eligible for a TOL with 1 previous low transverse incision were categorized according to whether they underwent an ERCD or TOL. A propensity score technique was used to develop ERCD and TOL groups with comparable baseline characteristics. Outcomes were assessed with conditional logistic regression. The rates of endometritis, operative injury, respiratory distress syndrome, and newborn infant infection were lower and the rates of hysterectomy and wound complication were higher in the ERCD group. Propensity score techniques can be used to generate comparable ERCD and TOL groups. Some types of maternal morbidity (such as hysterectomy) are higher; other types (such as operative injury) are lower in the ERCD group. Although the absolute risk is low, neonatal morbidity appears to be lower in the ERCD group.

Separate mnemonic effects of retrieval practice and elaborative encoding

Does retrieval practice produce learning because it is an especially effective way to induce elaborative encoding? Four experiments examined this question. Subjects learned word pairs across alternating study and recall periods, and once an item was recalled it was dropped from further practice, repeatedly studied, or repeatedly retrieved on repeated recall trials. In elaborative study conditions, subjects used an imagery-based keyword method (Experiments 1–2) or a verbal elaboration method (Experiment 3) to encode items during repeated study trials. On a criterial test 1week after the initial learning phase, repeated retrieval produced better long-term retention than repeated study even under elaborative study conditions. Elaborative studying improved initial encoding when it occurred prior to the first correct recall of an item, but while repeated retrieval enhanced long-term retention, elaboration produced no measurable learning when it occurred after successful retrieval. Experiment 4 used identical item word pairs (e.g., castle–castle) to reduce or eliminate verbal elaboration, and robust effects of repeated retrieval were still observed with these materials. Retrieval practice likely produces learning by virtue of mechanisms other than elaboration.

Intra- and Inter-Instrument Reliability of the Actiwatch 4 Accelerometer in a Mechanical Laboratory Setting

This study aimed to quantify the intra-and inter-instrument reliability of the Actiwatch 4 accelerometer (AW4) in a mechanical setting. Twenty seven AW4 were attached to an isokinetic dynamometer and subjected to angular acceleration for 30 min at 50 deg/sec representing moderate intensity (MPA condition) and 200 deg/sec representing vigorous intensity (VPA condition), with a repeat trial conducted. Reliability was assessed using coefficient of variation (CV), absolute percent error (APE), and intraclass correlation coefficients (ICC). Mean AW4 activity counts displayed acceptable reliability according to CV in both conditions (ConMPA: CVintra = 4.6%, APEintra = 6.6%, CVinter = 6.4%, APEinter = 5.2%; ConVPA: CVintra = 3.9%, APEintra = 5.6%, CVinter = 5.9%, APEinter = 4.7%). When counts were re-categorised into minutes of MPA and VPA, lower CV values were observed (ConMPA: CVintra = 3.2%, APEintra = 4.5%, CVinter = 4.3%, APEinter = 3.2%; ConVPA: CVintra = 0.0%, APEintra = 0.0%, CVinter = 0.0%, APEinter = 0.0%). When activity counts were re-categorised as minutes of MVPA, excellent reliability was observed (CVintra, APEintra, CVinter, and APEinter = 0.0%) in both conditions. Mean AW4 activity counts exhibit reliability statistics comparable to other accelerometers. Reliability is improved when activity counts are re-categorised as time spent in MPA and VPA, with greatest reliability obtained when counts are recategorised as time spent in MVPA. As MVPA is the subcomponent of physical activity most associated with health benefits it would appear that the AW4 is reliable for measuring time spent in this health enhancing intensity category, at least from testing in a mechanical laboratory setting.

Stimulus repetition probability effects on repetition suppression are position invariant for faces

It has been shown that the probability of face repetitions influences the magnitude of repetition-related response reductions (Summerfield et al., 2008), implying that perceptual expectations affect adaptation and repetition suppression processes in the human central nervous system. An unresolved question is whether probability effects are specific for the retinal position of the stimuli or affect stimulus processing globally, throughout the visual field. To address this question we tested whether face repetition probability affects fMRI adaptation (fMRIa) when the repeated stimuli are presented on the same retinal position, overlapping each other or when they are presented in opposite hemifields. Subjects were exposed to either two identical (repeated trial, RT) or two different (alternating trial, AT) face stimuli. Both types of trials were presented either in blocks consisting of 75% (repeated block, RB) or 25% (alternating block, AB) of RTs. We found that repetition probability influences fMRIa equally for overlapping and nonoverlapping arrangements: the signal reduction after RT was more pronounced in RB than in AB for both spatial arrangements of stimulus-pairs. This effect was present in bilateral fusiform and occipital face areas, as well as in the lateral occipital cortex. Our results support the role of stimulus repetition probability in determining fMRIa and shows that the effect is invariant to the retinal position of stimuli.

Asymmetric switch-costs and ERPs reveal facial identity dominance over expression

Previous studies on face processing have revealed an asymmetric overlap between identity and expression, as identity is processed irrespective of expression while expression processing partly depends on identity. To investigate whether this relative interaction is caused by dominance of identity over expression, participants performed familiarity and expression judgments during task switching. This paradigm reveals task-set dominance with a paradoxical asymmetric switch-cost (i.e., greater difference between switch and repeat trials when switching toward the dominant task). Event-related potentials (ERPs) were recorded to find the neural signature of the asymmetric cost. As expected, greater switch-cost was shown in the familiarity task with respect to response times, indicating its dominance over the expression task. Moreover, a left-sided ERP correlate of this effect was observed at the level of the frontal N2 component, interpreted as an index of modulations in endogenous executive control. Altogether, these results confirm the overlap between identity and expression during face processing and further indicate their relative dominance.

A comparison of the reliability of dynamic retinoscopy and subjective measurements of amplitude of accommodation

Dynamic retinoscopy (DR) is an objective technique for assessing maximum accommodative responsivity. The present study examined the test-retest reliability of this procedure when measuring the amplitude of accommodation (AA). In the first trial, the within-session repeatability of the AA was measured in 79 subjects between 18 and 30 years of age using DR and two subjective procedures, namely the modified push-down (MPD) and minus lens (ML) techniques. Data were collected by two different examiners. In a second trial, the inter-session repeatability of the AA was assessed in 76 subjects by a single evaluator with a time interval of 7 days between the first and second sessions. The repeatability, reproducibility and agreement between the methods were determined using the mean difference, 95% limits of agreement, intraclass correlation coefficient and concordance correlation coefficient. DR showed the lowest mean value of AA in each trial (average for the two trials = 7.44 D) while the equivalent mean values for the MPD and ML techniques were 9.84 and 9.43 D, respectively. Further, DR showed the best repeatability in both the repeatability trials and poorer inter-examiner agreement was observed for the MPD and ML procedures. The concordance correlation coefficient for DR-MPD, DR-ML and MPD-ML procedures were 0.32, 0.33 and 0.62, respectively for the within-session trial and 0.31, 0.36 and 0.76, respectively for the inter-session trial. The DR technique provides a more veridical measurement of the AA because it avoids the overestimation resulting from the depth-of-field. Moreover, the DR technique exhibited higher reproducibility, when compared with subjective methods. These differences may be important when evaluating accommodative dysfunctions or monitoring accommodative therapy. The fact that the DR procedure can be performed using standard clinical equipment makes this a valuable technique both for vision screening programs and routine eye care.

Sustained target-driven interference under optimal preparation in a cued task switching paradigm using orthogonal polynomial trend analysis (OPTA)

Event Abstract Back to Event Sustained target-driven interference under optimal preparation in a cued task switching paradigm using orthogonal polynomial trend analysis (OPTA) Alexander Provost1, Andrew Heathcote2, Scott Brown2, Sharna Jamadar3 and Frini Karayanidis1* 1 University of Newcastle, School of Psychology, Australia 2 University of Newcastle, School of Psychology, Australia 3 Monash University, School of Psychology and Psychiatry, Australia Dual process models of cognitive control posit the existence of both proactive and reactive control processes. Cued task switching paradigms have differentiated these processes by measuring ERPs linked to advance preparation during the cue-target interval (CTI) and ERPs linked to resolution of target-driven interference after target onset. Using Orthogonal Polynomial Trend Analysis (OPTA) to extract cue-locked ERP waveforms corresponding to semi-deciles of each participant’s RT distribution, Karayanidis et al. (2011, Psychophysiology, 48, 559–568) showed that proactive control involves both switch-specific and general task preparation processes. A significant residual RT switch cost remained even at the fastest semi-decile that was associated with greater proactive control, suggesting that reactive control may be required to resolve post-target interference even on optimally prepared trials. In this paper, we use OPTA to examine target-locked ERP waveforms associated with different levels of preparation. Fast ‘prepared’ switch trials (i.e., large cue-locked switch-positivity and small RT switch cost) showed no anterior N2 and a large prominent P3b. Slow ‘unprepared’ switch trials (i.e., small switch-positivity and large switch cost) showed a large anterior N2 and a very small P3b. Similar variability in N2 and P3b amplitude was evident across the RT distribution for repeat trials. At the fastest percentile, switch trials produced a larger N2 and smaller P3b than repeat trials, indicating that fully prepared switch trials continue to show greater interference than fully prepared repeat trials. These findings are consistent with the notion that proactive control can reduce but does not eliminate post-target interference for switch trials. Keywords: cognitive control, task switching, OPTA, ERP, interference control Conference: ACNS-2012 Australasian Cognitive Neuroscience Conference, Brisbane, Australia, 29 Nov - 2 Dec, 2012. Presentation Type: Oral Presentation Topic: Executive Processes Citation: Provost A, Heathcote A, Brown S, Jamadar S and Karayanidis F (2012). Sustained target-driven interference under optimal preparation in a cued task switching paradigm using orthogonal polynomial trend analysis (OPTA). Conference Abstract: ACNS-2012 Australasian Cognitive Neuroscience Conference. doi: 10.3389/conf.fnhum.2012.208.00184 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: 25 Oct 2012; Published Online: 17 Nov 2012. * Correspondence: Prof. Frini Karayanidis, University of Newcastle, School of Psychology, Newcastle, NSW 2308, Australia, frini.karayanidis@newcastle.edu.au 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 Alexander Provost Andrew Heathcote Scott Brown Sharna Jamadar Frini Karayanidis Google Alexander Provost Andrew Heathcote Scott Brown Sharna Jamadar Frini Karayanidis Google Scholar Alexander Provost Andrew Heathcote Scott Brown Sharna Jamadar Frini Karayanidis PubMed Alexander Provost Andrew Heathcote Scott Brown Sharna Jamadar Frini Karayanidis 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.

Aging and Random Task Switching: The Role of Endogenous Versus Exogenous Task Selection

Background/Study Context: Task switching research typically emphasizes two robust shifting effects between competing tasks: mixing costs (MCs), which indicate less efficient performance in mixed-task versus single-task conditions, and switch costs (SCs), which reflect differences between switch trials and repetition trials within mixed-task conditions. The current study examined age-related MC and SC influenced by the method of task selection in two procedures. Methods: Twenty-six young adults, 18 to 21 years of age (M = 18.4, SD = 1.1), and 25 older adults, 74 to 87 years of age (M = 80.3, SD = 5.4), participated as part of the Cognition, Health, and Aging Project (CHAP). Younger and older adults’ performed cued and voluntary task switching, requiring a random sequence of task changes, placing demands on externally versus internally directed processes. Results: Results indicated that SCs were not disproportionately larger for older adults during an exogenous switching condition, but large age differences in MCs were present beyond the degree predicted by differences in baseline speed. In an endogenous switching condition, small age differences were present both for MCs and SCs, although further age differences were evident in older adults’ reduced switch rates. Conclusion: These findings suggest that older adults are substantially slower at updating repeated task sets during exogenous switching, but partially counter these effects by adopting a more persistent within-set mode of processing during endogenous switching.

The bivalency effect: Evidence for flexible adjustment of cognitive control.

When bivalent stimuli (i.e., stimuli with features for two different tasks) appear occasionally, performance is slower on subsequent univalent stimuli. This "bivalency effect" reflects an adjustment of cognitive control arising from the more demanding context created by bivalent stimuli. So far, it has been investigated only on task switch trials, but not on task repetition trials. Here, we used a paradigm with predictable switches and repetitions on three tasks, with bivalent stimuli occasionally occurring on one task. In three experiments, we found a substantial bivalency effect for all trials with at least one source of conflict. However, this effect was reduced for the repetition trials sharing no features with bivalent stimuli, that is, for those without conflict. This confirms that the bivalency effect reflects an adjustment of cognitive control. The news is that this adjustment of cognitive control is sensitive to the presence of conflict, but neither to its amount nor to its source.

Stimulus repetition reduces stimulus encoding by small neuronal populations in macaque inferior temporal cortex

Event Abstract Back to Event Stimulus repetition reduces stimulus encoding by small neuronal populations in macaque inferior temporal cortex Dzmitry A. Kaliukhovich1 and Rufin Vogels1* 1 KU Leuven, Neuroscience, Belgium Stimulus repetition reduces spiking responses in macaque inferior temporal (IT) cortex, i.e. repetition suppression or adaptation. Single cell recording studies in V1 and V4 reported that adaptation improves stimulus encoding. Thus far it is not known whether the same holds true in IT, in particular given the apparently greater adaptation strength in IT compared to earlier visual areas. Here, we examined the effect of stimulus repetition on the accuracy of small populations of IT neurons to classify familiar images of objects. We recorded multi-unit activity with a laminar electrode (16 sites spaced 100 µm) in the rostral ventral bank of the superior temporal sulcus in 2 rhesus monkeys (N = 32 penetrations) while they were performing a passive fixation task. We presented 2 stimuli (A and B) successively, each for 500 ms, with an ISI of 500 ms. Trials consisted either of a repetition (AA or BB) of the same stimulus or of their alternation (AB or BA). Stimulus-selective adaptation was present in 90% of stimulus x responsive site combinations (N = 468; see Kaliukhovich and Vogels, 2012 for details). Machine learning-based classifiers (Support Vector Machines (SVM) and correlation-based classifier) were employed to decode stimulus identity (A vs. B) from the neuronal population responses (spike counts in an interval of 60-310 ms after stimulus onset per trial and site) of each penetration. Classifiers were trained using half of the data and tested using the remaining half. The SVM classifier showed significantly lower classification for the test compared to the adapter stimulus (mean across penetrations: 80% vs. 74%, P < 0.000005) in repetition trials. However, classification for test stimuli in alternation trials and when only one of the stimuli was adapted (e.g. A following A vs. B following A) did not differ significantly from that of the adapter. The correlation-based classifier produced highly similar results. Shuffling trial order of a stimulus across sites within a penetration, i.e. eliminating noise correlations, and using the SVM classifier produced similar effects, except that classification was significantly larger by ~2% (P < 0.0005). These data suggest that stimulus-specific adaptation in IT does not improve coding of objects repeated in short stimulus sequences but instead may impair it. Acknowledgements This work was supported by Fonds voor Wetenschappelijk Onderzoek Vlaanderen (G.0644-08), Geconcerteerde Onderzoeksactie (GOA/10/019), Interuniversitaire Attractiepool (IUAP) and Programma Financiering (PF 10/008). For the computation of classifiers we used the infrastructure of the VSC – Flemish Supercomputer Center, funded by the Hercules Foundation and the Flemish Government – department EWI. References Kaliukhovich, D. A., & Vogels, R. (2012). Stimulus repetition affects both strength and synchrony of macaque inferior temporal cortical activity. Journal of Neurophysiology, 107, 3509-3527 Keywords: adaptation, inferior temporal cortex, stimulus discriminability, repetition suppression, macaque monkey Conference: Belgian Brain Council, Liège, Belgium, 27 Oct - 27 Oct, 2012. Presentation Type: Poster Presentation Topic: Higher Brain Functions in health and disease: cognition and memory Citation: Kaliukhovich DA and Vogels R (2012). Stimulus repetition reduces stimulus encoding by small neuronal populations in macaque inferior temporal cortex. Conference Abstract: Belgian Brain Council. doi: 10.3389/conf.fnhum.2012.210.00106 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: 21 Aug 2012; Published Online: 12 Sep 2012. * Correspondence: Dr. Rufin Vogels, KU Leuven, Neuroscience, Leuven, 3000, Belgium, rufin.vogels@kuleuven.be 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 Dzmitry A Kaliukhovich Rufin Vogels Google Dzmitry A Kaliukhovich Rufin Vogels Google Scholar Dzmitry A Kaliukhovich Rufin Vogels PubMed Dzmitry A Kaliukhovich Rufin Vogels 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.