Indirect Semantic Priming Research Articles

Multimodal neuroimaging evidence for looser lexico-semantic networks in schizophrenia:Evidence from masked indirect semantic priming

It has been hypothesized that schizophrenia is characterized by overly broad automatic activity within lexico-semantic networks. We used two complementary neuroimaging techniques, Magnetoencephalography (MEG) and functional Magnetic Resonance Imaging (fMRI), in combination with a highly automatic indirect semantic priming paradigm, to spatiotemporally localize this abnormality in the brain.Eighteen people with schizophrenia and 20 demographically-matched control participants viewed target words (“bell”) preceded by directly related (“church”), indirectly related (“priest”), or unrelated (“hammer”) prime words in MEG and fMRI sessions. To minimize top-down processing, the prime was masked, the target appeared only 140 ms after prime onset, and participants simply monitored for words within a particular semantic category that appeared in filler trials.Both techniques revealed a significantly larger automatic indirect priming effect in people with schizophrenia than in control participants. MEG temporally localized this enhanced effect to the N400 time window (300–500 ms) — the critical stage of accessing meaning from words. fMRI spatially localized the effect to the left temporal fusiform cortex, which plays a role in mapping of orthographic word-form on to meaning. There was no evidence of an enhanced automatic direct semantic priming effect in the schizophrenia group.These findings provide converging neural evidence for abnormally broad highly automatic lexico-semantic activity in schizophrenia. We argue that, rather than arising from an unconstrained spread of automatic activation across semantic memory, this broader automatic lexico-semantic activity stems from looser mappings between the form and meaning of words.

The impact of auditory white noise on semantic priming

It has been proposed that white noise can improve cognitive performance for some individuals, particularly those with lower attention, and that this effect may be mediated by dopaminergic circuitry. Given existing evidence that semantic priming is modulated by dopamine, this study investigated whether white noise can facilitate semantic priming. Seventy-eight adults completed an auditory semantic priming task with and without white noise, at either a short or long inter-stimulus interval (ISI). Measures of both direct and indirect semantic priming were examined. Analysis of the results revealed significant direct and indirect priming effects at each ISI in noise and silence, however noise significantly reduced the magnitude of indirect priming. Analyses of subgroups with higher versus lower attention revealed a reduction to indirect priming in noise relative to silence for participants with lower executive and orienting attention. These findings suggest that white noise focuses automatic spreading activation, which may be driven by modulation of dopaminergic circuitry.

Modeling the Flesh of God: Semantic Hyperpriming and the Teonancátl Cults of Mexico

The ritualistic use of the ancient psychoactive sacrament teonanacatl, or “The Flesh of God,” represents an integral aspect of pre-colonial Mesoamerican culture and continues, in various syncretic forms, to this day. Providing a brief history of various tribes of Mexico known to utilize Psilocibe species within a shamanic context, focusing primarily on the Mazatec people of Oaxaca, this paper attempts to utilize contemporary cognitive research of psilocybin to better understand and contextualize the ancient teonanacatl ceremony; specifically, research into psilocybin’s induction of the hyperpriming state of cognition. Hyperpriming, or indirect semantic priming, is characterized by its expansive branched hierarchical associative structure within the semantic network and presents us with a valid and useful explanatory framework with which to interpret many of the reported psychological, linguistic, and perceptual effects underlying the traditional teonanacatl ceremony.

An investigation of gender differences in semantic processing in individuals with high schizotypy

Semantic processing deficits may underlie thought disorder in schizophrenia. Cognitive Disorganisation (CD) in schizotypy is a thought disorder analogue. This study established CD was related to abnormal strategic semantic processing on an indirect semantic priming task. There were no gender differences. It also confirms the importance of replicating underpowered studies.

Greater neuronal responses during automatic semantic processing in schizophrenia.

A core feature of schizophrenia is a disturbance of associative processes. To date, no functional MRI studies have investigated semantic priming in schizophrenia under experimental conditions that measure automatic, as opposed to strategic, processing. The present study's focus was to investigate hemodynamic responses during indirect semantic priming at a short stimulus onset asynchrony (i.e., 350 ms), conditions which are considered to be a particularly sensitive measure of automatic spreading activation during semantic processing and of the associative disturbances in schizophrenia. Seventeen individuals with DSM-IV, schizophrenia and 15 comparison participants underwent functional scanning while performing a lexical decision task on directly related, indirectly related, unrelated, and word/nonword pairs. A random-effects region of interest analysis within a priori temporal and frontal regions was performed. Whereas comparison individuals exhibited hemodynamic suppression in response to priming, individuals with schizophrenia exhibited hemodynamic enhancement. Relative to the comparison group, these enhancements were observed in the left fusiform and superior temporal gyri for indirectly related word pairs relative to unrelated pairs. Greater priming-related responses within temporal regions may reflect increased and prolonged automatic spreading activation during semantic processing in schizophrenia.

Attention and available long-term memory in an activation-based model

The influence of attention on memorizing related items and on available long-term memory (ALTM) was explored, showing that N400 of no-memory items was more negative than that of the memory item. The results of the category comparison task indicated that information processing under attention-driven in WM determined the availability of related long-term memory, i.e., specific content, which was formerly concerned or ignored, yielding different indirect semantic priming effects. These indicate that the orientation of conceptual attention leads the related representations of LTM to diverse activation patterns, supporting the activation-based model.

Why all the confusion? Experimental task explains discrepant semantic priming effects in schizophrenia under “automatic” conditions: Evidence from Event-Related Potentials

The schizophrenia research literature contains many differing accounts of semantic memory function in schizophrenia as assessed through the semantic priming paradigm. Most recently, Event-Related Potentials (ERPs) have been used to demonstrate both increased and decreased semantic priming at a neural level in schizophrenia patients, relative to healthy controls. The present study used ERPs to investigate the role of behavioral task in determining neural semantic priming effects in schizophrenia. The same schizophrenia patients and healthy controls completed two experiments in which word stimuli were identical, and the time between the onset of prime and target remained constant at 350 ms: in the first, participants monitored for words within a particular semantic category that appeared only in filler items (implicit task); in the second, participants explicitly rated the relatedness of word-pairs (explicit task). In the explicit task, schizophrenia patients showed reduced direct and indirect semantic priming in comparison with healthy controls. In contrast, in the implicit task, schizophrenia patients showed normal or, in positively thought-disordered patients, increased direct and indirect N400 priming effects compared with healthy controls. These data confirm that, although schizophrenia patients with positive thought disorder may show an abnormally increased automatic spreading activation, the introduction of semantic decision-making can result in abnormally reduced semantic priming in schizophrenia, even when other experimental conditions bias toward automatic processing.

Acute and Chronic Effects of Ketamine on Semantic Priming

Acute administration of the N-methyl-D-aspartate receptor antagonist ketamine induces schizophrenia-like symptoms in healthy volunteers; furthermore, a window on ketamine's chronic effects is provided by regular recreational users. The current study utilized both acute ketamine administration in healthy volunteers and chronic ketamine abusers to investigate semantic processing, one of the key cognitive deficits in schizophrenia. Semantic processing was examined using a semantic priming paradigm. In experiment 1, acute effects of low (75 ng/mL) and high (150 ng/mL) ketamine doses were compared in a placebo-controlled double-blind independent group design with 48 participants. In experiment 2, 19 regular recreational ketamine users were compared with 19 ketamine-naive polydrug controls and 26 non-drug-using controls. In both experiments, semantic priming parameters were manipulated to distinguish between ketamine's effects on (1) automatic and strategic processing and (2) the facilitation and inhibition components of semantic priming for strongly (directly) related primes and targets. Acute effects of ketamine on semantic priming for weakly (indirectly) related primes and targets were also assessed in experiment 1. Acutely, ketamine impaired the employment of strategic mechanisms but not automatic processing within both the direct and indirect semantic priming tasks. Acute ketamine administration also induced clear schizophrenia-like symptoms. Schizotypy traits in the cognitive and perceptual domains tended to correlate with increased semantic priming in long-term ketamine users. In summary, acute and chronic ketamine-induced changes partially mirrored the findings on semantic priming in schizophrenia.

Lack of noradrenergic modulation of indirect semantic priming.

Norepinephrine and dopamine are both believed to affect signal-to-noise in the cerebral cortex. Dopaminergic agents appear to modulate semantic networks during indirect semantic priming, but do not appear to affect problem solving dependent on access to semantic networks. Noradrenergic agents, though, do affect semantic network dependent problem solving. We wished to examine whether noradrenergic agents affect indirect semantic priming. Subjects attended three sessions: one each after propranolol (40 mg) (noradrenergic antagonist), ephedrine (25 mg) (noradrenergic agonist), and placebo. During each session, closely related, distantly related, and unrelated pairs were presented. Reaction times for a lexical decision task on the target words (second word in the pair) were recorded. No decrease in indirect semantic priming occurred with ephedrine. Furthermore, across all three drugs, a main effect of semantic relatedness was found, but no main effect of drug, and no drug/semantic relatedness interaction effect. These findings suggest that noradrenergic agents, with these drugs and at these doses, do not affect indirect semantic priming with the potency of dopaminergic drugs at the doses previously studied. In the context of this previous work, this suggests that more automatic processes such as priming and more controlled searches of the lexical and semantic networks such as problem solving may be mediated, at least in part, by distinct mechanisms with differing effects of pharmacological modulation.

Lack of Noradrenergic Modulation of Indirect Semantic Priming

Norepinephrine and dopamine are both believed to affect signal-to-noise in the cerebral cortex. Dopaminergic agents appear to modulate semantic networks during indirect semantic priming, but do not appear to affect problem solving dependent on access to semantic networks. Noradrenergic agents, though, do affect semantic network dependent problem solving. We wished to examine whether noradrenergic agents affect indirect semantic priming. Subjects attended three sessions: one each after propranolol (40 mg) (noradrenergic antagonist), ephedrine (25 mg) (noradrenergic agonist), and placebo. During each session, closely related, distantly related, and unrelated pairs were presented. Reaction times for a lexical decision task on the target words (second word in the pair) were recorded. No decrease in indirect semantic priming occurred with ephedrine. Furthermore, across all three drugs, a main effect of semantic relatedness was found, but no main effect of drug, and no drug/semantic relatedness interaction effect. These findings suggest that noradrenergic agents, with these drugs and at these doses, do not affect indirect semantic priming with the potency of dopaminergic drugs at the doses previously studied. In the context of this previous work, this suggests that more automatic processes such as priming and more controlled searches of the lexical and semantic networks such as problem solving may be mediated, at least in part, by distinct mechanisms with differing effects of pharmacological modulation.

Lion – tiger – stripes: Neural correlates of indirect semantic priming across processing modalities

"Lions" do not have "stripes". However, via the word "tiger" both words are closely connected within the semantic network. With the present study we pursued two goals: to detect neural correlates of (1) directly and indirectly related word pairs by means of priming, and (2) to assess the effect of presentation modality. Stimuli were presented with a short SOA of 350 ms as subjects performed a lexical decision task during fMRI measurement. Four experimental conditions were compared: directly related (picture-frame), indirectly related (anvil-nail), unrelated (steamboat-needle) and nonword trials (chalk-edan), presented in a uni- (word-word) and cross-modal (auditory-word) version. Behavioral data revealed a modality-independent priming effect only for direct semantic priming. On a neural level, directly linked words led to left-lateralized activations in fronto-temporo-parietal areas. Indirect priming led to right-hemispheric fronto-parietal signal changes. Common areas of activation for uni- and cross-modal priming were found within the left middle temporal gyrus and right precuneus for direct priming and within the right insula for indirect priming. The comparison of the semantic distances (direct>indirect) showed one region activated modality-independent: the precuneus. Direct priming is associated with activation clusters corresponding to a large left-lateralized network. Indirect priming recruits right-hemispheric regions, reflecting widespread semantic fields and attentional components. The modality-independent comparison of direct and indirect priming revealed common areas of activation supporting an amodal rather than multiple semantic systems. The activation related to semantic distances underpins the special role of the precuneus. This region is involved in semantic priming and association processing whereas episodic memory contents might be addressed.

Evidence of Semantic Processing Abnormalities in Schizotypy Using an Indirect Semantic Priming Task

Semantic processing abnormalities are predicted to underlie thought disorder in schizophrenia. This study investigated semantic processing in relation to cognitive disorganization in schizotypy, a thought disorder analog. Schizotypy was measured in 53 healthy university students using the Oxford-Liverpool Inventory of Feelings and Experiences questionnaire. All participants completed 2 semantic priming tasks; direct and indirect (referring to the degree of association between word pair stimuli) and within each task, half of the stimuli were presented with a short time interval between prime and target presentation and half with a long time interval. Correlational analyses suggested that increasing cognitive disorganization was significantly associated with greater priming on the indirect tasks only. Separate analyses of the male and female data also revealed that men scoring highly on cognitive disorganization exhibited more indirect priming and less direct priming, whereas the female schizotypy data showed no significant correlations with either priming task. These findings are indicative of abnormal indirect priming in schizotypy, which was more pronounced in the male participant group. The findings of the present study further support the proposal that semantic processing is abnormal in schizophrenia, without the presence of potentially confounding factors that have limited research with clinical populations.

An Event-Related Brain Potential Study of Direct and Indirect Semantic Priming in Schizophrenia

Following a meaningful prime stimulus, schizophrenia patients have been hypothesized to exhibit impaired neurophysiological activation of related concepts in general, and/or supranormal activation of weakly related concepts in particular, within semantic memory. The former abnormality may occur at longer intervals, and the latter at shorter intervals, after the prime. The authors tested these hypotheses using the N400 event-related brain potential as a probe of activation of concepts in semantic memory. Event-related potentials were recorded in 16 schizophrenia patients and 16 normal comparison subjects who viewed prime words, each followed by a target that was a directly (strongly) related word, indirectly (weakly) related word, unrelated word, or nonword, in a lexical-decision task. Equal numbers of each target type were presented 300 and 750 msec after the prime. In the comparison subjects, N400 amplitude was largest (most negative) following unrelated targets, intermediate after indirectly related targets, and smallest after directly related targets. In contrast, patients' N400 amplitudes did not differ between these target types, reflecting larger amplitudes following both directly and indirectly related targets in patients than in comparison subjects; these findings held regardless of prime-to-target stimulus-onset asynchrony. Within patients, at the longer asynchrony, larger N400 amplitudes after directly and indirectly related targets correlated with positive psychotic symptoms. The results suggest hypoactivation of strongly and weakly related concepts following a meaningful stimulus, regardless of interval, in schizophrenia. An N400 index of this hypoactivation correlated with severity of delusions, suggesting a role for abnormal semantic processing in their pathogenesis.

Neural Evidence for Faster and Further Automatic Spreading Activation in Schizophrenic Thought Disorder

It has been proposed that the loose associations characteristic of thought disorder in schizophrenia result from an abnormal increase in the automatic spread of activation through semantic memory. We tested this hypothesis by examining the time course of neural semantic priming using event-related potentials (ERPs). ERPs were recorded to target words that were directly related, indirectly related, and unrelated to their preceding primes, while thought-disordered (TD) and non-TD schizophrenia patients and healthy controls performed an implicit semantic categorization task under experimental conditions that encouraged automatic processing. By 300-400 milliseconds after target word onset, TD patients showed increased indirect semantic priming relative to non-TD patients and healthy controls, while the degree of direct semantic priming was increased in only the most severely TD patients. By 400-500 milliseconds after target word onset, both direct and indirect semantic priming were generally equivalent across the 3 groups. These findings demonstrate for the first time at a neural level that, under automatic conditions, activation across the semantic network spreads further within a shorter period of time in specific association with positive thought disorder in schizophrenia.

An electrophysiological investigation of indirect semantic priming

In two experiments, direct and indirect semantic priming were measured using event-related potentials. In Experiment 1, participants rated the relatedness between prime and target on a seven-point scale. In Experiment 2, participants simply read the primes and targets as they monitored for a semantic category in probe filler items. Significant direct and indirect N400 priming effects were observed in both experiments. In Experiment 1, the indirect N400 priming effect remained significant when indirectly related and unrelated word pairs were matched for participants' explicit relatedness judgments. In both experiments, the indirect N400 priming effects were preserved when indirectly related and unrelated word pairs were matched on more global and objective measures of semantic similarity. These findings are discussed in the context of current theoretical models of semantic memory and semantic priming.

Working Memory Capacity, Indirect Semantic Priming, and Stroop Interference: Pattern of Interindividual Prefrontal Performance Differences in Healthy Volunteers.

Using neuropsychological models of prefrontal function, the authors investigated the pattern of interindividual prefrontal performance differences in healthy volunteers. Using a correlation and an extreme group approach, they compared verbal and visuospatial working memory capacity with performance on the Stroop interference task as a measure of executive control and on the direct and indirect semantic priming tasks as a measure of semantic access. Subjects with low visuospatial working memory capacity exhibited increased Stroop interference Subjects with low verbal memory capacity showed increased priming and Stroop interference only. The study shows that prefrontal functioning varies interindividually, forming patterns of performance differences. These findings suggest that working memory, executive control, and semantic retrieval are functionally related to some extent.

The effect of backward masking on direct and indirect semantic priming in patients with Parkinson’s disease and in healthy individuals

The effect of backward masking on direct and indirect semantic priming in patients with Parkinson’s disease and in healthy individuals

Indirect semantic priming in schizophrenic patients

Deficits in working memory (WM) are a core feature of schizophrenia (SZ) and other psychotic disorders. We examined brain activity during WM in persons at clinical high risk (CHR) for psychosis.Thirty-seven CHR and 34 healthy control participants underwent functional MRI (fMRI) on a 3.0 T scanner while performing an N-back WM task. The sample included a sub-sample of CHR participants who had no lifetime history of treatment with psychotropic medications (n = 11). Data were analyzed using SPM8 (2-back > 0-back contrast). Pearson correlations between brain activity, symptoms, and WM performance were examined.The total CHR group and medication-naive CHR sub-sample were comparable to controls in most demographic features and in N-back WM performance, but had significantly lower IQ. Relative to controls, medication-naïve CHR showed hyperactivity in the left parahippocampus (PHP) and the left caudate during performance of the N-back WM task. Relative to medication-exposed CHR, medication naïve CHR exhibited hyperactivity in the left caudate and the right dorsolateral prefrontal cortex (DLPFC). DLPFC activity was significantly negatively correlated with WM performance. PHP, caudate and DLPFC activity correlated strongly with symptoms, but results did not withstand FDR-correction for multiple comparisons. When all CHR participants were combined (regardless of medication status), only trend-level PHP hyperactivity was observed in CHR relative to controls.Medication-naïve CHR exhibit hyperactivity in regions that subserve WM. These regions are implicated in studies of schizophrenia and risk for psychosis. Results emphasize the importance of medication status in the interpretation of task - induced brain activity.

Increased automatic spreading of activation in thought-disordered schizophrenic patients

Previous research on semantic priming in schizophrenia has produced conflicting findings. While several studies provided evidence for an enhanced cognitive spreading of activation in schizophrenia patients with formal thought disorder, other research has failed to replicate. The aim of the present study was to resolve some of the ambiguities in the literature. Thirty-two schizophrenic patients (12 with and 20 without symptoms of formal thought disorder according to the PANADSS) and 65 healthy controls were compared in a semantic priming task using word pronunciation. Irrespective of baseline condition (neutral or unrelated condition) patients with formal thought disorder (TD) exhibited a significantly greater indirect semantic priming effect than both non-TD patients and healthy controls. Known confounding variables such as length of illness, neuroleptic dosage and psychomotor slowness did not moderate priming. Results further strengthen the spreading activation model of formal thought disorder put forward by Maher/Manschreck and Spitzer. Data indicate that hyper-priming is not confined to lexical decision tasks. Possible reasons why several studies have failed to replicate greater priming in TD schizophrenic patients are discussed.

'Hyper-priming' in thought-disordered schizophrenic patients.

A number of studies have suggested that indirect semantic priming is enhanced in thought-disordered schizophrenics. However, research on direct semantic priming has produced conflicting results. The aim of the present study was to resolve some of the ambiguities of previous findings. For the present study, 44 schizophrenic patients were split according to the presence of associative loosening into a positive thought-disordered (TD) and non-positive thought-disordered (NTD) group. Thirty healthy subjects and 36 psychiatric patients served as controls. Schizophrenics displayed increased indirect semantic priming compared with psychiatric controls. When subtyping the sample, TD-patients exhibited significantly enhanced indirect semantic priming compared with healthy and psychiatric controls as well as NTD-patients. Overall slowing was found to be independent of priming effects. Medication, age and chronicity of the schizophrenic illness did not modulate priming. In line with Spitzer and Maher it is inferred that disinhibited semantic networks underlie formal thought disorder in schizophrenia. For future research, it would be appropriate to: employ indirect semantic priming rather than direct semantic priming conditions; and, pay more attention to potential moderators of the priming effect, most importantly, the prime display duration and the length of the stimulus onset asynchrony.