Visual Memory and the Brain

Friday, May 9, 2008, 1:00 – 3:00 pm Orchid 1

Organizer: Marian Berryhill (University of Pennsylvania)

Presenters: Lynn C. Robertson (University of CA, Berkeley & VA), Yaoda Xu (Yale University), Yuhong Jiang (University of Minnesota), Vincent Walsh (University College London), Marian Berryhill (University of Pennsylvania)

Symposium Description

Focus:

Visual memory describes the relationship between perceptual processing and the storage and retrieval of the resulting neural representations. Visual memory occurs over a broad time range of scenes across eye movements – to years – in order to visually navigate to a previously visited location or to recognize an old friend. How does the brain encode, store, and retrieve these representations? What neural mechanism limits the capacity and resolution of visual memory? Do the same neural areas participate in short-term and long-term visual memory? Do particular neural regions, such as the intraparietal sulcus, participate only in visual memory, or does it have a more generally role in attentionally demanding tasks such as binding and multi-object tracking? Are different brain areas critically involved in storing different visual materials, such as simple colors or complex scenes? These topics have only begun to be studied; the purpose of this symposium is to discuss the latest research and current problems facing our understanding of visual memory. Investigators in this area of research employ a variety of techniques such as the lesion method (neuropsychology and TMS), neuroimaging (fMRI, ERP), and behavioral studies.

Timeliness:

The finding that the intraparietal sulcus may limit the capacity of visual short-term memory is an example of a topic that has been published in prominent journals, thereby fueling new studies and generating broad interest. Moreover, this general topic of the neural basis of visual memory relates to several other timely topics in the visual cognition literature including: neural areas involved in multi-object tracking, attention, scene perception, navigation, and long-term memory.

Audience:

This symposium would be accessible to a broad VSS Audience as it includes both perceptual and cognitive processing. Furthermore, by including speakers who come from a variety of methodological backgrounds, including neuropsychology and neuroimaging. Both students and seasoned researchers will find it of interest. The audience will gain a better understanding of visual cognition and of current methodological techniques being used to understand brain-behavior relationships.

Abstracts

Forms of visual representation in unattended space: neuropsychological evidence

Lynn C. Robertson, Thomas Van Vleet, UC Berkeley, VA

Although there is a great deal of evidence that undetected information can affect subsequent performance (e.g., priming), the nature of the memory representation that produces this effect is not well understood. In a series of studies with patients who suffer from left sided neglect and/or extinction from right hemisphere damage, we show that feature displays prime a subsequent central target equally well whether the features were more or less likely to be detected. Conversely, conjunction displays prime more when they are more likely to be detected. These results will be discussed as they relate to visual storage of undetected stimuli and how memory representations differ with attention.

Dissociable parietal mechanisms supporting visual short-term memory for objects

Yaoda Xu, Yale University

In this talk, I will show that visual short-term memory (VSTM) storage is mediated by distinctive posterior brain mechanisms, such that VSTM capacity is determined both by a fixed number of objects and by object complexity. These findings not only advance our understanding of the neural mechanisms underlying VSTM, but also have interesting implications to theories on visual object perception.

Speaker 3

Yuhong Jiang, U. Minnesota

Dr. Jiang will discuss behavioral and fMRI data on visual short-term memory, with an emphasis on synthesis of findings.

Migrating Memories: Remembering what comes next

Vincent Walsh, UCL

Memory, along with attention, imagery, learning, getting grants and awareness is sometimes assumed to be a high level function. There is, however, an increasing “migration” of functions from higher to lower areas as we ask more diffiucult questions of the sensory cortex. For example, what were once considered “cognitive” contours with neural correlates in IT can be inferred from the responses of V1 or V2 neurons and visual imagery and visual awareness require V1. It is becoming increasingly clear that a similar migration of complexity is occuring in memory and we can now rightly speak about sensory memory in visual cortex. I will discuss experiments which explore the role of visual areas in short term memory and visual priming. Specifically I will discuss the effects of interfering with memory processes by applying TMS over visual area V5, the frontal eye fields and the parietal cortex.

When was I Where?

Marian E. Berryhill & Ingrid R. Olson, U. Pennsylvania, Temple University

The perceptual deficits following dorsal stream damage are well-known, i.e. hemispatial neglect, Balint’s syndrome. However, accumulating evidence suggests that these same cortical regions are involved in processing ‘when’ as well as ‘where’. In a series of studies examining unilateral and bilateral parietal patients we have observed visual, spatial working memory as well as autobiographical and constructive memory impairments. These data suggest that these patients have cognitive deficits that parallel their perceptual deficits. In this talk, we will discuss the effects of dorsal stream damage on visual perception as well as the effects on stored representations in short-term and long-term memory.