Visual short-term memory and its clinical application in patients with impaired memory functions

Group photo of researchers from Vision and Eye Research Unit, Anglia Ruskin University in front of a desk with laptop

Professor Shahina Pardhan, Dr Ian van der Linde, Professor Peter Bright, Keisha Notice and Dr Raju Sapkota. Collaboration between the Vision & Eye Research Unit (VERU) and the Departments of Computing & Technology and the Brain and Cognition Group, Department of Psychology.

Current activities

  • To examine the effects of age on visual short-term memory.

  • To investigate how visual short-term memory is influenced by various parameters including central/peripheral visual field, object familiarity, and the type of a visual task used (such object-recall and location-recognition).

  • To examine the role of VSTM in guiding fixational and saccadic eye movements.

  • To develop visual short-term memory based tests for the detection of early cognitive decline in patients with Alzheimer's disease.

  • To identify whether changing the stimulus physical characteristics such as luminance, contrast, size, etc. can help in memory rehabilitation.

Outcomes

Our work on visual short-term memory using unfamiliar objects has shown how visual short-term memory is affected when deprived of support from visual long-term memory. 

We are one of the few to demonstrate how relatively few (less than two) unfamiliar, nonverbal objects can be held in visual short-term memory compared to the commonly cited four to six-object capacity for familiar stimuli. We have shown how visual short-term memory can be improved by presenting objects at familiar locations. 

Furthermore, we have shown that while fixating an object, the visual information that is processed from peripheral retina (although may not be distinctly identifiable) affects our memory for the centrally fixated target. We have also shown how visual short-term memory can be improved by manual tapping performed at the location of to-be-remembered objects. 

Our early findings from the study investigating the effect of normal aging on visual short-term memory show significant age differences in visual short-term memory for object recall and location recognition, and that visual short-term memory is more often than not populated with partial traces of memory items. Collectively, these findings provide a significant contribution towards gaining a greater understanding of basic and higher order properties of visual short-term memory, together with behaviourally implied dorsal-ventral processing differences within the human brain. 

Our research on semantic dementia has challenged the widely held position that this is a condition which solely affects the semantic memory system. Over time, other cognitive functions become compromised as the disease spreads laterally and posteriorly in the brain. Our studies of patients with organic amnesia (secondary to herpes simplex encephalitis and alcoholic Korsakoff syndrome) offer a more complex picture of the role of the hippocampi (and the wider medial temporal cortex) in memory storage and forgetting. Functional and structural neuroimaging investigations of visual object processing in normal and brain damaged individuals have provided strong evidence for a hierarchical system in which low-level visual features are processed in more posterior occipito-temporal cortex culminating in complex conjunctions of features represented in more anterior regions. This system is thought to provide the neural substrate for fine-grained visual and conceptual level understanding of our environment (and the objects within it).

Publications

Sapkota, R., Pardhan, S., and van der Linde, I. (2013). Manual tapping enhances visual short-term memory performance where visual and motor coordinates correspond, British Journal of Psychology, 104, 249-264. 
Sapkota, R., Pardhan, S., and van der Linde, I. (2011a). The impact of extra-foveal information on visual short-term memory for object-position. Journal of Cognitive Psychology, 23, 574-585.
Sapkota, R., Pardhan, S., and van der Linde, I. (2011b). Object-position binding in visual short-term memory for sequentially presented unfamiliar stimuli. Perception, 40, 538-548.
Bright, P., Moss, H. E., Stamatakis, E. A., and Tyler, L. K. (2008). Longitudinal studies of semantic dementia: The relationship between structural and functional changes over time. Neuropsychologia, 46, 2177-2188.
Bright, P., Moss, H.E., Longe, O., Stamatakis, E.A., and Tyler, L. K. (2007). Conceptual Structure Modulates Anteromedial Temporal Involvement in Processing Verbally Presented Object Properties. Cerebral Cortex, 17, 1066-1073.