Testing the Identification/Production Hypothesis of Implicit Memory in Schizophrenia: The Role of Response Competition.

OBJECTIVES: Previous evidence indicates that patients with schizophrenia exhibit reduced repetition priming in production tasks (in which each response cue engenders a competition between alternative responses), but not in identification tasks (in which each response cue allows a unique response). However, cross-task comparisons may lead to inappropriate conclusions, because implicit tests vary on several dimensions in addition to the critical dimension of response competition. The present study sought to isolate the role of response competition, by varying the number of solutions in the context of the same implicit tasks. METHODS: Two experiments investigated the performance of patients with schizophrenia and healthy controls in the high-competition and low-competition versions of word-stem completion (Exp.1) and verb generation (Exp.2). RESULTS: Response competition affected both the proportions of stems completed (higher to few-solution than to many-solution stems) and the reaction times of verb generation (slower to nouns having no dominant verb associates than to nouns having one dominant verb associate). Patients with schizophrenia showed significant (non-zero) priming in both experiments: crucially, the magnitude of this facilitation was equivalent to that observed in healthy controls and was not reduced in the high-competition versions of the two tasks. CONCLUSIONS: These findings suggest that implicit memory is spared in schizophrenia, irrespective of the degree of response competition during the retrieval phase; in addition, they add to the ongoing debate regarding the validity of the identification/production hypothesis of repetition priming.

Does pointing facilitate the recall of serial positions in visuospatial working memory?

The present study examined the question of whether pointing enhances the serial recall of visuospatial positions. Thirty-six participants were presented with 40 target arrays varying in length from five to eight items, with each position appearing sequentially in red for 1 s. The task was to reproduce the order of presentation of the positions on a blank matrix. Results showed that, for five-, six-, and seven-item arrays, order memory was significantly better in the passive view than in the pointing condition, and the serial position curves displayed both recency and priority effects. Interestingly, the advantage of the passive-view condition was more pronounced in the early than in the late positions. For eight-item arrays, no significant differences were found between the passive view and the pointing conditions. Overall, the present data provide no evidence in support of the view that pointing facilitates the recall of serial positions.

Pointing towards visuospatial patterns in short-term memory: differential effects on familiarity- and recollection-based judgments.

Previous studies have indicated that pointing toward to-be-remembered visuospatial patterns enhances short-term memory (STM) when the presentation of pointing and no-pointing trials is mixed (Chum et al., 2007; Dodd & Shumborski, 2009; Rossi-Arnaud et al., 2012). By contrast, when presentation is blocked, pointing has inhibitory effects on memory (Dodd & Shumborski, 2009; Rossi-Arnaud et al., 2012). In the present study, we demonstrated that pointing has different effects on short-term recollection- and familiarity-based judgments, depending on the length of the visuospatial patterns (5- vs. 7-item arrays) and the interval between the encoding and test phases (2 vs. 5 s). More specifically, pointing decreased the accuracy of recollection-based judgments for 5-item arrays, but not for 7-item arrays (this negative effect did not interact with interval length). In contrast, pointing facilitated familiarity-based judgments when the interval between the study and test phases was 5 s, but not when it was 2 s (this positive effect did not interact with pattern length). We proposed that the negative effects might be accounted for by the simultaneous recruitment of attention resources in the planning and execution of pointing movements. As a consequence, executive resources are diverted from the primary memory task, resulting in a less efficient use of attention-demanding retrieval strategies, like chunking. By contrast, the positive effects on familiarity judgments might reflect the unitization of the to-be-remembered items into a single shape.

Is conceptual implicit memory impaired in schizophrenia? Evidence from lexical decision and category verification.

INTRODUCTION: Implicit memory tasks differ along two orthogonal dimensions, tapping the relative involvement of perceptual/conceptual and identification/production processes. Previous studies have documented a dissociation between perceptual (spared) and conceptual (impaired) implicit memory, using in the latter case a production task (category exemplar generation), in which there is high response competition during the retrieval phase. The present study sought to determine whether the perceptual/conceptual dissociation held when comparing two identification tasks, in which there is no response competition at retrieval. METHODS: In two experiments, repetition priming was assessed in 44 schizophrenic patients and 46 healthy controls in lexical decision (a test based on perceptual identification processes) and category verification (a test based on conceptual identification processes). RESULTS: Schizophrenic patients achieved a priming as high as that of controls in the lexical decision task. In contrast, only controls exhibited significant priming in the category verification task. CONCLUSIONS: It is concluded that schizophrenia is associated with a specific deficit in conceptual implicit memory, irrespective of the degree of response competition in the test phase.

The attentional boost effect in schizophrenia.

The present study reports 2 experiments examining the Attentional Boost Effect (ABE) in schizophrenic patients and matched healthy controls, using visual and verbal materials. The ABE refers to the surprising finding that, in a divided attention condition, images and words encoded with targets are remembered better than images and words encoded with distractors. Unlike controls (who showed the typical ABE), schizophrenic patients reported no memory advantage for stimuli presented together with targets in the divided attention condition. On the other hand, the interference effect on the recognition of stimuli presented with distractors was not exacerbated in patients (as compared with controls). In line with the dual-task interaction model proposed by Swallow and Jiang (2013), the absence of a significant facilitation indicates that schizophrenic patients have a deficit in the process of attentional enhancement triggered by target detection. A number of neural mechanisms potentially underlying this impairment are discussed, as well as implications for the characterization of the attentional deficits involved in schizophrenia.