CNS 2013 - Mini-Symposium Session 3

THE EFFECTS OF WORKING MEMORY TRAINING ON BRAIN AND BEHAVIOR

Monday, April 15, 1:30 - 3:00 pm, Garden Room

Chair: Bornali Kundu, University of Wisconsin - Madison

Co-Chair: Bradley R. Postle, University of Wisconsin - Madison

Speakers: Susanne M. Jaeggi, Christos Constantinidis, Torkel Klingberg, Bornali Kundu

The past decade has witnessed an explosion of interest in working memory training, largely because successful demonstrations have refuted the long-held assumption that working memory capacity is an inherent trait, insensitive to environmental influence. Cognitive training has also shown the potential to treat neurological and psychiatric disorders. Of late, however, progress has been slowed by questions of how, or even whether, working memory training may transfer to untrained tasks. This mini-symposium will directly address this by bringing together four perspectives from which working memory training has been studied. Jaeggi will address the theoretical (and practical) bases for predict- ing the transfer of working memory training to untrained tasks. Constantinidis will characterize the effects of working memory training on single-neuron responses and neuronal population dynamics, as measured in the non-human primate. Klingberg will consider genetic and developmental factors that influence variation in working memory training effects, and their neural correlates as measured through human brain imaging. Finally, Kundu will present evidence that a causal factor underlying working memory training effects is training-related changes in effective connectivity within task-relevant networks. Collectively, these talks will provide a broad foundation from which to evaluate the training literature. Emergent from it will be a principled understanding of what factors determine the success, or otherwise, of a training protocol. Thus, this mini-symposium will bring timely attention to a domain of cognitive neuroscience that is simultaneously among the most exciting and most controversial, and one that holds great potential for translation to the clinic, the classroom, and beyond.

TRANSFER OF WORKING MEMORY TRAINING: THEORETICAL AND PRACTICAL CONSIDERATIONS

Susanne M. Jaeggi; University of Maryland - College Park

Working memory training and the study of transfer and plasticity are among the current hot topics in cognitive neuroscience. While some have argued that there is no evidence for transfer as a function of cognitive training, we and others have pointed out that working memory training can be, indeed, effective, but that there are important mediating and moderating factors that might determine training success. In this talk, I will provide evidence for the efficacy of several working memory interventions developed in our laboratories, and review the emerging literature coming from other groups. I will show data that demonstrate transfer to non-trained tasks throughout the lifespan, that is, in young adults, in old adults, in typically developing children, as well as children with ADHD. I will also discuss the neural correlates that accompany working memory training as observed with our interventions. However, I will also point out that transfer effects can be elusive, and that some of the effects do not seem to be easily replicated. I will argue that instead of taking inconsistencies as a proof for a lack of efficacy, researchers need to develop innovative approaches to move the cognitive training literature beyond the simple question of whether or not training is effective, and to address questions of underlying mechanisms, individual differences, and training features and parameters that might mediate and moderate the efficacy of training.

EFFECTS OF WORKING MEMORY TRAINING AT THE NEURONAL LEVEL

Christos Constantinidis, Xue-Lian Qi; Wake Forest School of Medicine

Neurons in the lateral prefrontal cortex are active during the execution of cognitive tasks that require working memory. Prior studies suggest that the activity of single neurons is shaped by learning, though much is unknown about how training alters neural activity and cortical organization. To address this question, we performed neurophysiological recordings in non-human primates before and after they were trained to perform working memory tasks. Prior to any training, prefrontal neurons responded to stimuli, exhibited persistent activity after their offset, and differentiated between matching and non-matching stimuli presented in sequence. After training, more neurons were recruited by the stimuli and exhibited higher firing rates, particularly during the delay periods of the task. Operant stimuli that needed to be recognized in order to perform the task elicited higher overall rates of responses, while the variability of individual discharges and correlation of discharges between neurons decreased after training. New information was incorporated in the activity of a small population of neurons highly specialized for the task and in a larger population of neurons that exhibited modest task related information, while information about other aspects of stimuli remained present in neuronal activity. Despite such changes, the relative selectivity of the dorsal and ventral aspect of the lateral prefrontal cortex was not altered with regard to spatial and non-spatial stimuli. These results indicate the nature of neuronal changes induced by training and the limits of plasticity of cortical areas mediating cognitive tasks.

TRAINING OF WORKING MEMORY

Torkel Klingberg; Karolinska Institute

Impaired working memory is associated with low academic performance and with distractability and inattention in clinically defined groups, such as in ADHD, but the same associations are also relevant in the general population. Klingberg and collaborators have developed and tested a computerized method for training working memory (Kling- berg et al. 2002, 2005, Klingberg 2010), which showed, for the first time, that working memory capacity can be enhanced. Moreover, improving working memory also decreases the symptoms of inattention in everyday life. This has now been confirmed by several independent research groups using the same method, which also allows comparison of effect sizes across different ages and patient groups. The method can be used as an instrument for studying brain plasticity. Klingberg and collegues have shown that training of work- ing memory changes brain activity in frontal and parietal regions, and is associated with changes in the density of dopamine D1-receptors in the cortex. Polymorphisms of the DAT-1 gene affect the relative benefit of cognitive training, which is consistent with a key role of dopamine for train- ing-related plasticity. Questions for future research include: which tasks are more effective, what training paradigms are more effective and what are the factors promoting plasticity?

CHANGES IN CORTICAL EFFECTIVE CONNECTIVITY UNDERLIE WORKING MEMORY TRAINING

Bornali Kundu, Bradley R. Postle; University of Wisconsin - Madison

Although long considered a natively endowed and fixed trait, working memory ability has recently been shown to improve with intensive training. What remains controversial and poorly understood, however, are the factors underlying this improvement, and the extent to which working memory training gains transfer to other cognitive tasks. To explore these questions, we trained subjects on either an adaptive n-back working memory task or a control task (Tetris) for five hours per day, five days per week, for five weeks. Pre- and post-training measures assessed individual performance on visuospatial short-term memory (VSTM), selective attention, interference control, and several psycho- metric tasks. Here we will present evidence from electro- physiology (EEG) and simultaneous transcranial magnetic stimulation (TMS) and EEG that both near and far transfer of working memory training to other cognitive tasks is sup- ported by changes in task-related effective connectivity in frontoparietal and extrastriate networks that are engaged by both the trained and transfer tasks. One consequence of this is greater efficiency of stimulus processing, as evidenced by training-related changes in the ‘contralateral delay activity’, an EEG index of individual differences in short-term memory capacity and visual search performance. These pat- terns of training and transfer highlight the role of common neural systems in determining individual differences in many aspects of visuospatial cognition.