Effects of Memory Load and Distraction on Performance and Event-Related Slow Potentials in a Visuospatial Working Memory Task

Brain electrical activity related to working memory was recorded at 15 scalp electrodes during a visuospatial delayed response task. Participants (N = 18) touched the remembered position of a target on a computer screen after either a 1 or 8 sec delay. These memory trials were compared to sensory trials in which the target remained present throughout the delay and response periods. Distractor stimuli identical to the target were briefly presented during the delay on 30% of trials. Responses were less accurate in memory than sensory trials, especially after the long delay. During the delay slow potentials developed that were significantly more negative in memory than sensory trials. The difference between memory and sensory trials was greater at anterior than posterior electrodes. On trials with distractors, the slow potentials generated by memory trials showed further enhancement of negativity, whereas there were minimal effects on accuracy of performance. The results provide evidence that engagement of visuospatial working memory generates slow wave negativity with a timing and distribution consistent with frontal activation. Enhanced brain activity associated with working memory is required to maintain performance in the presence of distraction.

[1]  Y. Agid,et al.  Cortical dysfunction and schizophrenic deficit. Preliminary findings with the delayed reaction paradigm , 1992, European psychiatry.

[2]  S. Funahashi,et al.  Working memory and prefrontal cortex , 1994, Neuroscience Research.

[3]  A. Benton,et al.  Frontal Lobe Function and Dysfunction , 1991 .

[4]  A. Diamond,et al.  The Development and Neural Bases of Memory Functions as Indexed by the AB and Delayed Response Tasks in Human Infants and Infant Monkeys a , 1990, Annals of the New York Academy of Sciences.

[5]  Edward E. Smith,et al.  Spatial working memory in humans as revealed by PET , 1993, Nature.

[6]  Y. Agid,et al.  Delayed response tasks and prefrontal lesions in man—Evidence for self generated patterns of behaviour with poor environmental modulation , 1993, Neuropsychologia.

[7]  P. Goldman-Rakic,et al.  Neuronal activity related to saccadic eye movements in the monkey's dorsolateral prefrontal cortex. , 1991, Journal of neurophysiology.

[8]  C. Rossouw,et al.  Lattice Images of Solid Xenon Precipitates in Aluminum at Room Temperature , 1985, Science.

[9]  R. Roberts,et al.  Prefrontal cognitive processes: Working memory and inhibition in the antisaccade task. , 1994 .

[10]  A. Baddeley.  Human Memory: Theory and Practice, Revised Edition , 1990 .

[11]  C. Braun,et al.  Working memory and the Self-Ordered Pointing Task: further evidence of early prefrontal decline in normal aging. , 1993, Journal of clinical and experimental neuropsychology.

[12]  M. Annett.  A classification of hand preference by association analysis. , 1970, British journal of psychology.

[13]  P. Goldman-Rakic,et al.  Functional magnetic resonance imaging of human prefrontal cortex activation during a spatial working memory task. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[14]  P. Goldman-Rakic,et al.  Alpha 2-adrenergic mechanisms in prefrontal cortex associated with cognitive decline in aged nonhuman primates. , 1985, Science.

[15]  A. Baddeley,et al.  The Spot-the-Word test: a robust estimate of verbal intelligence based on lexical decision. , 1993, The British journal of clinical psychology.

[16]  P. Goldman-Rakic,et al.  D1 dopamine receptors in prefrontal cortex: involvement in working memory , 1991, Science.

[17]  H Hämäläinen,et al.  A spatial oculomotor memory-task performance produces a task-related slow shift in human electroencephalography. , 1995, Electroencephalography and clinical neurophysiology.

[18]  T. Goldberg,et al.  Isolating the Mnemonic Component in Spatial Delayed Response: A Controlled PET15O-Labeled Water Regional Cerebral Blood Flow Study in Normal Humans , 1996, NeuroImage.

[19]  P. Goldman-Rakic,et al.  Dorsolateral prefrontal lesions and oculomotor delayed-response performance: evidence for mnemonic "scotomas" , 1993, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[20]  R. Depue,et al.  Facilitation of Working Memory in Humans by a D2 Dopamine Receptor Agonist , 1992, Journal of Cognitive Neuroscience.

[21]  M. Oscar-Berman,et al.  Clinical and experimental approaches to varieties of memory. , 1991, The International journal of neuroscience.

[22]  S. Tipper,et al.  Behavioural Goals Determine Inhibitory Mechanisms of Selective Attention , 1994 .

[23]  Richard S. J. Frackowiak,et al.  Brain regions associated with acquisition and retrieval of verbal episodic memory , 1994, Nature.

[24]  Sohee Park,et al.  Schizophrenics show spatial working memory deficits. , 1992, Archives of general psychiatry.

[25]  J. Grafman,et al.  Distinctions and similarities among working memory processes: an event-related potential study. , 1992, Brain research. Cognitive brain research.

[26]  P. Goldman-Rakic,et al.  Mnemonic coding of visual space in the monkey's dorsolateral prefrontal cortex. , 1989, Journal of neurophysiology.

[27]  B. J. Casey,et al.  Activation of the prefrontal cortex in a nonspatial working memory task with functional MRI , 1994, Human brain mapping.

[28]  T. Sawaguchi,et al.  Catecholaminergic effects on neuronal activity related to a delayed response task in monkey prefrontal cortex. , 1990, Journal of neurophysiology.

[29]  Sohee Park,et al.  Association of working memory deficit and eye tracking dysfunction in schizophrenia , 1993, Schizophrenia Research.

[30]  M Hallett,et al.  Induction of errors in a delayed response task by repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex. , 1994, Neuroreport.

[31]  W Lang,et al.  Cortical DC potential shifts accompanying auditory and visual short-term memory. , 1992, Electroencephalography and clinical neurophysiology.

[32]  R. Bartus,et al.  Recent memory in aged non-human primates: hypersensitivity to visual interference during retention. , 1979, Experimental aging research.

[33]  Edward E. Smith,et al.  Dissociation of Storage and Rehearsal in Verbal Working Memory: Evidence From Positron Emission Tomography , 1996 .

[34]  J. Stamm,et al.  Electrical stimulation of monkeys' prefrontal cortex during delayed-response performance. , 1969, Journal of comparative and physiological psychology.

[35]  D. Ruchkin,et al.  Working memory and preparation elicit different patterns of slow wave event-related brain potentials. , 1995, Psychophysiology.

[36]  Bao-Ming Li,et al.  Delayed-response deficit induced by local injection of the alpha 2-adrenergic antagonist yohimbine into the dorsolateral prefrontal cortex in young adult monkeys. , 1994, Behavioral and neural biology.

[37]  W Ritter,et al.  Event-related brain potential evidence for a verbal working memory deficit in multiple sclerosis. , 1994, Brain : a journal of neurology.