Tian-xiao Yang

Prospective memory in schizophrenia: Further clarification of nature of impairment

Prospective memory (PM) refers to the ability to execute a delayed intention and is different from retrospective memory (RM) in its nature and underlying mechanism (e.g., intention formation, maintenance, detection of PM cue and intention execution). Although preliminary studies have found PM impairment in patients with schizophrenia, the nature and magnitude of this problem in this clinical group is not yet fully known. The current study aimed to further clarify the nature of this impairment in schizophrenia. Fifty-four patients with schizophrenia and fifty-four healthy volunteers matched on demographic variables, IQ and executive functions took part in the study. Time-, event-, and activity-based PM tasks and a set of neurocognitive tests were administered to the participants. Results showed that patients with schizophrenia performed significantly worse on all sub-types of PM tasks, even after controlling for neurocognitive functions such as working memory, verbal memory, visual memory, and executive function. These findings suggest PM deficit is a primary deficit rather than a secondary consequence of neurocognitive impairments in schizophrenia. Analysis found that PM deficits may be mainly due to the impairment of the cue detection and intention retrieval stage.

The Development of Prospective Memory in Typically Developing Children

OBJECTIVE This study aimed to use specifically designed tasks to capture time-based, activity-based, and event-based prospective memory (PM) performance in typically developing school-age children. METHOD Two PM tasks (Fishing Game & Happy Week) were used to examine the developmental patterns of PM in these children. Retrospective memory (RM) was also examined in these tasks. A total of 120 children aged between 7 and 12 years (10 girls and 10 boys in each age band) were recruited. Tests of working memory, inhibition, and IQ were also administered. RESULTS The age effect on PM accuracy was significant, with improvements identified between ages 7 to 8 and 10 to 11 years. For both tasks, performance on the time-based PM task was significantly poorer than that on the event-based PM task, which in turn was significantly poorer than that on the activity-based PM task. In terms of errors, results indicated that while errors associated with the PM component of the tasks decreased with age, errors associated with the RM component showed an inverted-U shape. The different patterns of errors suggest qualitative as well as quantitative differences in PM development in children. Finally, IQ, working memory, and inhibition were found to relate to PM when age was partialed out. CONCLUSIONS Results of the study highlight the importance of contextual cues, such as activities and events, for prospective remembering in children. In addition, they have provided a general picture of PM development in school-age children and have implications for educators and parents.

Benefit of enactment over oral repetition of verbal instruction does not require additional working memory during encoding.

For this research, we used a dual-task approach to investigate the involvement of working memory in following written instructions. In two experiments, participants read instructions to perform a series of actions on objects and then recalled the instructions either by spoken repetition or performance of the action sequence. Participants engaged in concurrent articulatory suppression, backward-counting, and spatial-tapping tasks during the presentation of the instructions, in order to disrupt the phonological-loop, central-executive, and visuospatial-sketchpad components of working memory, respectively. Recall accuracy was substantially disrupted by all three concurrent tasks, indicating that encoding and retaining verbal instructions depends on multiple components of working memory. The accuracy of recalling the instructions was greater when the actions were performed than when the instructions were repeated, and this advantage was unaffected by the concurrent tasks, suggesting that the benefit of enactment over oral repetition does not cost additional working memory resources.

Examining the role of working memory resources in following spoken instructions

ABSTRACT This study investigated the involvement of working memory (WM) in following spoken instructions using concurrent tasks designed to disrupt components of the Baddeley and Hitch WM model [Baddeley, A. D., & Hitch, G. J. (1974). Working memory. In G. H. Bower (Ed.), The psychology of learning and motivation: Advances in research and theory (Vol. 8, pp. 47–89). New York, NY: Academic Press]. In each of three experiments, participants were presented with sequences of instructions to be either verbally repeated or physically performed using relevant objects. Backward counting, articulatory suppression, and eye closure during instruction encoding all disrupted recall, and also impaired recall of the linkage between movements and objects. Recall of actions was more accurate when they were physically enacted than repeated verbally, an advantage that was not affected by concurrent tasks. These findings indicate that aspects of the recall of spoken instructions including the binding of constituent movements to objects draw on multiple WM resources. The benefits of physical enactment of the instructed sequence do not appear to depend on the components of WM investigated in these studies.

Neural correlates of prospective memory in individuals with schizotypal personality features

OBJECTIVE Prospective memory (PM) refers to the ability to remember to perform actions in the future. Schizophrenia spectrum disorders show impairments in PM but neural correlates of these impairments remain unclear. The present study aimed to examine brain activation during PM to identify impairments in individuals with schizotypal personality features. METHOD Nineteen participants with schizotypal features and 22 healthy controls participated in a functional MRI experiment while performing a PM task. RESULTS Results showed that the prefrontal cortex (including Brodmann Area [BA] 10), middle temporal gyrus, and precuneus were activated when performing the PM task compared with baseline. The schizotypal and control groups did not differ in behavioral PM performance. However, participants with schizotypal features showed decreased activations in the inferior and medial frontal lobes (BA 45, and 8). CONCLUSIONS These results confirmed that the PM network involves prefrontal cortex, including BA 10. The lower activation in prefrontal cortex of individuals with schizotypal features when performing a PM task indicates brain activation abnormality. Notably, this abnormality may occur in the absence of any behavioral manifestation. Our findings support the hypothesis of frontal lobe involvement in PM deficits observed in individuals with schizotypal features.

The influence of input and output modality on following instructions in working memory

Following instructions is an important component of learning and has been shown to rely on working memory. This study examined the ability to follow instructions within working memory under varying input and output modalities. In Experiment 1, participants heard, read, or viewed demonstration of short sequences of instructions, and recalled either by oral repetition or physical enactment. There was a significant main effect of encoding, showing superior recall performance when instructions were demonstrated relative to spoken or written presentation. Experiment 2 examined whether recall is further improved when instructions are presented both in spoken and demonstrated form, relative to single modality presentation. The advantage for demonstration over spoken instructions was replicated, and dual input was superior to spoken instructions. However, dual input did not bring extra benefit compared to demonstration of instructions. We also observed a significant enacted-retrieval recall advantage. These findings suggest effects of both input and output modalities on the ability to remember and follow instructions in working memory. Outcomes substantially inform the underexplored but important new area of action-based working memory and its links to embodied cognition, with implications for pedagogic practice.

Aberrant default mode network homogeneity in patients with first-episode treatment-naive melancholic depression

BACKGROUND Melancholic depression is a relatively homogenous subtype of major depressive disorders (MDD). The condition has several endogenous symptoms and represents strong biological components. However, its specific neurobiological mechanisms remain unknown. Previous neuroimaging findings indicated that default mode network (DMN) is closely related to MDD. The present study examined the network homogeneity (NH) of the DMN in patients with melancholic MDD. METHODS A total of 33 first-episode, treatment-naive melancholic MDD patients and 32 healthy controls underwent a resting-state functional magnetic resonance imaging scan. The data were analyzed using the NH method. RESULTS Compared with healthy controls, patients with melancholic MDD showed low NH values in the right middle temporal gyrus and temporal pole (MTG/TP). The abnormal NH of this region and clinical characteristics were not correlated. CONCLUSION Abnormal NH pattern of DMN exists in patients with melancholic MDD. This feature may be part of the pathophysiological basis of this disorder.

Neural Correlates of Prospective Memory Impairments in Schizophrenia

OBJECTIVE Prospective memory (PM) refers to the ability to remember to carry out intended actions after a delay. PM impairments are common in schizophrenia patients and are thought to be related to their prefrontal cortex dysfunction; however, this has not yet been examined directly in the research literature. The current study aimed to examine abnormalities in brain activation during PM task performance in schizophrenia patients. METHOD Twenty-two schizophrenia patients and 25 matched healthy controls were scanned in a 3-T MRI machine while performing a PM task. RESULTS The results showed that compared to the healthy controls, schizophrenia patients performed significantly worse on the PM task. Furthermore, they exhibited decreased brain activation in frontal cortex including the right superior frontal gyri (Brodmann area 10), and other related brain areas like the anterior cingulate gyrus, parietal and temporal cortex, including precuneus, and some subcortext, including parahippocampal gyrus and putamen. CONCLUSIONS These findings confirm the involvement and importance of the prefrontal cortex in PM and show evidence of hypofrontality in schizophrenia patients while performing a PM task.

Impaired Memory for Instructions in Children with Attention-Deficit Hyperactivity Disorder Is Improved by Action at Presentation and Recall

Children with attention deficit hyperactivity disorder (ADHD) often fail to comply with teacher instructions in the classroom. Using action during presentation or recall can enhance typically developing children’s abilities to complete multi-step instruction sequences. In this study, we tested the ability to following instructions in children with ADHD under different conditions to explore whether they show the same beneficial effects of action. A total of 24 children with ADHD and 27 typically developing children either listened to or viewed demonstrations of instructions during encoding, and then either verbally repeated or physically performed the sequences during recall. This resulted in four conditions: spoken-verbal, spoken-enacted, demonstration-verbal, and demonstration-enacted. Children with ADHD were significantly impaired in all conditions of the following instructions task relative to the typically developing group. Both groups showed an enacted-recall advantage, with superior recall by physical performance than oral repetition. Both groups also benefitted from demonstration over spoken presentation, but only when the instructions were recalled verbally. These findings suggest that children with ADHD struggle to complete multi-step instructions, but that they benefit from action-based presentation and recall in the same way as typically developing children. These findings have important implications for educators, suggesting that motor-based methods of instruction-delivery might enhance classroom learning both for children with and without developmental disorders.

Time-based but not event-based prospective memory remains impaired one year after the onset of schizophrenia: A prospective study

BACKGROUND Prospective memory (PM) deficits have been consistently found in people with schizophrenia. Although there is evidence to suggest that PM deficits may be putative markers for schizophrenia, no longitudinal study has investigated the persistence of PM deficits. AIMS We examined whether PM deficits persist after the onset of schizophrenia, and compared the trajectories of time- and event-based PM performance 12 months after illness onset. We also examined whether the association between PM and clinical symptoms changes over time 12 months after illness onset. METHOD We recruited 58 individuals with first-episode schizophrenia for a 12-month follow-up study. Comparison participants were 37 healthy individuals who were matched in terms of demographics and intelligence with the patient group. PM functions and clinical symptoms were measured at baseline, the sixth month, and the twelfth month, using a computerized PM task and the Positive and Negative Syndrome Scale. RESULTS People with schizophrenia showed a gradual improvement in both time- and event-based PM 12 months after illness onset. However, compared to event-based PM, deficit in time-based PM persisted and was relatively stable. At baseline, PM functions were not associated with clinical symptoms. However, an association between time-based PM and PANSS positive and general symptoms emerged 12 months after the onset of schizophrenia. CONCLUSION People with first-episode schizophrenia exhibit persistent time-based PM deficit. Our findings support that PM deficit, in particular, time-based deficit, may be a putative neuropsychological marker of schizophrenia.