Proactive interference in Working Memory - neural correlates

Pamięć robocza jest jednym z najważniejszych konstruktów teoretycznych w szeroko pojętej dziedzinie jaką jest cognitive neuroscience. Dlatego zrozumienie procesów z nią związanych na poziomie ich mózgowego podłoża wydaje się tak istotne. Wiele badań wskazuje, że jednym z procesów ważnych dla funkcjonowania pamięci roboczej jest przezwyciężanie interferencji. Dlatego manipulacja poziomem interferencji proaktywnej w zadaniu powinna różnicować wyniki osiągane przez osoby o różnej sprawności pamięci roboczej. Celem tej pracy było zweryfikowanie hipotezy o udziale interferencji proaktywnej w pamięci roboczej na poziomie mózgowych korelatów tego procesu. Ośrodki w mózgu związane z tym procesem są w przybliżeniu poznane. Najważniejszym w tym kontekście wydaje się być dolny zakręt czołowy lewej półkuli, głównie z rejonie 45 pola Brodmanna. Do badania wykorzystano funkcjonalny rezonans magnetyczny. Zastosowano paradygmat zadania na rozpoznanie bodźca, niezwykle często stosowany w badaniach mózgowego podłoża interferencji.Working memory is one of the most important theoretical constructs in a domain of cognitive neuroscience. For that reason understanding neural underpinnings of these processes appears necessary. Numerous researches indicate that one of the most significant processes for working memory functioning is interference resolution. Therefore, manipulating proactive interference level ought to differentiate results gained by participants with different working memory capacity. An aim of this research was to check a hypothesis about a proactive interference contribution in working memory on neural level. Brain regions connected with this process are areapproximately studied. Especially left inferior frontal gyrus seems to be the most important, predominantly in the around 45th Brodmann’s area. In this fMRI study an item recognition task was used, a paradigm that is predominantly used in brain studies of the resolution of proactive interference

A validation of the Polish version of the Coma Recovery Scale-Revised : CRSR

PRIMARY OBJECTIVE: The aim of this study was to determine the validity of the Polish version of the Coma Recovery Scale-Revised (CRS-R). METHODS AND DESIGN: Two trained raters, A and B, administered CRS-R on a group of 20 patients with severe brain injury (median age ± SD, 38.0 ± 14.39 years). Both rater A and rater B completed their assessment on day 1, and rater A repeated their assessment on day 2. Inter-rater and test-retest reliability were evaluated with an intra-class correlation coefficient and Spearman rank correlation. Internal consistency was estimated with Cronbach's α. Agreement in diagnostic impression was determined using Cohen's κ. RESULTS: Inter-rater reliability for CRS-R total scores and test-retest reliability was excellent: (ρ = 0.76, p < 0.001) and (ρ = 0.92, p < 0.001), respectively. Inter-rater diagnostic agreement was good (κ = 0.72, p < 0.001). Inter-rater reliability for subscales was fair to excellent. Internal consistency was excellent (Cronbach's α = 0.85). CONCLUSION: The Polish version of CRS-R can be administered reliably by trained raters and can successfully differentiate between vegetative state (VS), minimally conscious (MCS), and patients emerging from a minimally conscious state (EMCS)

Training subjective experience in binocular rivalry

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Disorders of consciousness in view of neuroimaging

Patients after severe brain injury are often unable to communicate, move on their own or show evidence of a purposeful behaviour, yet at the same time they may remain conscious. Such states are referred to as disorders of consciousness. Their clinical diagnosis, as based on complex behavioural criteria, is still prone to error and may lead to ambiguous cases. This article is an overview of the recent experimental approaches aimed at the assessment of the structure and function of the central nervous system, based on neuroimaging and employing the current knowledge regarding the mechanisms of consciousness. All these approaches are aimed at identifying the most efficient measure to enable a reliable diagnosing. The first approach is based on structural imaging that provides information on the organisation and state of neural connections within the brain. Other approaches are functional studies divided into passive and active ones. Passive paradigms evaluate the ability of the neural networks in the patient’s brain to sustain consciousness without them having to take part in an experimental task, while the active ones enable the assessment of the state of consciousness on the basis of neural correlates of volitional activities recorded as the patient performs mental tasks. The latter approach rests on an assumption that volitional activity requires conscious processing and cannot be explained in terms of stereotypic reaction to stimulation. While a significant number of approaches presented herein works quite well with respect to differentiating the states on the group level, still only a few of them allow such differentiation on the level of an individual patient. On the latter level, the most important challenge (when it comes to choose a particular care for a patient) could be carried out by a complementary use of several methods at the same time or the evaluation of brain function based on various neuroimaging techniques (EEG and fMRI)

The response relevance of visual stimuli modulate the P3 component and the underlying sensorimotor network

The functional meaning and neural basis of the P3b component of ERPs are still under debate. One of the main issues is whether P3b reflects only stimulus-related processes (stimulus evaluation hypothesis) or response-related processes as well (stimulus-response or S-R link activation hypothesis). Here, we conducted an EEG experiment examining whether P3b may indeed reflect an S-R link activation, followed by an fMRI experiment in which we explored the brain areas and functional connectivity possibly constituting the neural basis of these sensorimotor links. In both experiments, two successive visual stimuli, S1 and S2, were presented with a 1 sec interval, and responses were defined either by S1 or S2, while participants responded only after S2 onset. The obtained EEG results suggest that P3b may be interpreted in terms of the S-R link activation account, although further studies are needed to disentangle P3-related activity from overlapping anticipatory activity. The obtained fMRI results showed that processing of the relevant S1 involved activation of a distributed postero-anterior sensorimotor network, and increased strength of functional connectivity within this network. This network may underlie activation of the S-R links, thus possibly also the P3b component, forming a bridging step between sensory encoding and response execution.info:eu-repo/semantics/publishe

The role of levels of processing in disentangling the ERP signatures of conscious visual processing

We aimed to distinguish electrophysiological signatures of visual awareness from other task-related processes through manipulating the level of processing of visual stimuli. During an event-related EEG experiment, 36 subjects performed either color (low-level condition) or magnitude (high-level condition) evaluations of masked digits. Participants also assessed subjective visibility of each stimulus using the Perceptual Awareness Scale (PAS). Mean amplitude of the components of interest was analyzed (VAN − 140–240 ms; LP − 380–480 ms) with weighted regression mixed model. In the VAN component time window the mean amplitude correlated with PAS rating in both conditions. Mean amplitude in the LP time window correlated with PAS ratings in the high-level condition, but not in the low-level condition. Our results support the temporal unfolding of ERP makers of conscious processing, with an early component reflecting the initial perceptual experience and a late component being a correlate of the conscious experience of non-perceptual information.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

The levels of perceptual processing and the neural correlates of increasing subjective visibility

According to the levels-of-processing hypothesis, transitions from unconscious to conscious perception may depend on stimulus processing level, with more gradual changes for low-level stimuli and more dichotomous changes for high-level stimuli. In an event-related fMRI study we explored this hypothesis using a visual backward masking procedure. Task requirements ma- nipulated level of processing. Participants reported the magnitude of the target digit in the high- level task, its color in the low-level task, and rated subjective visibility of stimuli using the Perceptual Awareness Scale. Intermediate stimulus visibility was reported more frequently in the low-level task, confirming prior behavioral results. Visible targets recruited insulo-fronto-parietal regions in both tasks. Task effects were observed in visual areas, with higher activity in the low- level task across all visibility levels. Thus, the influence of level of processing on conscious perception may be mediated by attentional modulation of activity in regions representing fea- tures of consciously experienced stimuli.SCOPUS: ar.jinfo:eu-repo/semantics/publishe