Groups of thought disordered (TD) and non-thought disordered (NTD) schizophrenic patients, unipolar affective patients and normal controls performed a lexical decision task involving the recognition of words immediately preceded (primed) by either an associated or an unrelated word. Significant increments in recognition speed in the associated prime condition were found in all groups, with significantly greater gain by TD schizophrenics than by others. These findings are consistent with network models of associational activation and lend support to an attentional deficit hypothesis for schizophrenic language functioning.
"However, the bivariate cross-subject correlational analysis between speed (reciprocal of RT) and accuracy reveals insignificant correlation coefficient (CC=-0.058, p=0.73), suggesting that the present behavioral patterns (i.e., RT and ER) are not likely confounded by SAT (Manschreck et al., 1988; Salthouse and Hedden, 2002). Moreover, since all comparisons on EEG data between correct and error trials were conducted on RT-matched trials and separately investigated in the congruent and incongruent conditions, they should also minimize the interference from SAT, if any, on identified EEG patterns. "
[Show abstract][Hide abstract] ABSTRACT: Performance errors have been attributed to distinct neural mechanisms in different tasks. Two temporally and physiologically dissociable neural patterns prior to errors, i.e., pre-stimulus alpha (8–13 Hz) power indicative of sustained attention and post-stimulus N2 amplitude indicative of cognitive control, have been widely (but independently) reported in many studies. However, it is still largely unknown whether these two neural mechanisms for error commission exist in a single task at the same time and, if so, whether they can be probed simultaneously and how they lead to response accuracy (collectively or separately). To this end, we measured high-density electroencephalography (EEG) signals in a color-word matching Stroop task. We quantified both patterns on EEG data from individual stimulus condition (congruent or incongruent), as well as on pooled data from both conditions. Enhanced pre-stimulus alpha power for errors was identified over the parieto-occipital area in the congruent condition and the pooled data. Reduced post-stimulus N2 amplitude was only revealed in the incongruent condition. More importantly, for the first time, a balanced interaction between these two EEG patterns was revealed in correct trials, but not in error trials. These findings suggest that errors in one task could occur due to distinct neural mechanisms, e.g., poor sustained attention, poor cognitive control, or missed balance between these two. The present results further suggest that the detection of neural patterns related to different neural mechanisms could be complicated by other modulation factors, such as stimulus condition. Therefore, more than one neural marker should be simultaneously monitored to effectively predict imminent errors.
"For example, Mednick indicated that individuals who focus on strong semantic associations would be less able to provide new ideas than individuals who consider more distant semantic association in reaction to a stimulus. This hypothesis has been verified in several studies (e.g., Friedman, Fishback, Förster, & Werth, 2003; Manschreck et al., 1988). For this reason, we wanted to explore if the inhibition function could in fact have an effect on the strength of semantic activation. "
"The popular approach is that the enhanced meaning proximity effect among schizophrenic participants is due to malfunctioning in the control and management systems, and actually reflects the difficulty in inhibition processes [23,36-40]. Other views claim that the central problem of schizophrenics does not revolve around difficulties in inhibitive processes, but rather around strong activation of the associations [4,41]. Also, there is a different approach that suggests the focus should be on the difficulty of the patients to allocate attention resources adequately . "
[Show abstract][Hide abstract] ABSTRACT: Previous research has yielded evidence for enhanced semantic priming in formal thought-disordered schizophrenia patients, a result that fits well with the hypothesis of disinhibited processes of spreading activation in this population.
The current study examined whether hyper priming among schizophrenia patients is an outcome of further spreading of activation of a node or a result of farther activation of nodes in the semantic network. We also try to shed light on the fate of this activation.
The present study tested this hypothesis by using semantic and identical priming in two different experiments. SOA (stimulus onset asynchrony) was manipulated (240 ms vs. 740 ms) within block. It is assumed that among healthy individuals, performance relies on a balance between activation and inhibition processes, contrary to in schizophrenic individuals. In order to examine this hypothesis, we compared formal thought-disordered schizophrenia patients, non thought-disordered schizophrenia patients, and healthy controls.
For thought-disordered schizophrenia patients, we found a large positive semantic effect and identical priming effect (129 ms and 154 ms, respectively) only with short SOA. SOA and type of priming did not modulate priming effects in the control groups.
This result supports the claim that there is a lack of inhibitory processes among thought-disordered patients. Hyper priming in the thought-disorder group may be an outcome of hyper activation followed by rapid decay below baseline threshold.
PLoS ONE 12/2013; 8(12):e82882. DOI:10.1371/journal.pone.0082882 · 3.23 Impact Factor
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