Overall, our research interests involve using techniques of experimental psychology and cognitive neuroscience to understand the mechanisms underlying visual perception and memory and how these break down in healthy and diseased aging.
The functioning of brain systems can be measured in several ways during perception and memory. Three from our lab include examining behavioral performance through experimental and standard neuropsychological testing, examining the electrical activity of the brain through scalp electroencephalographic (EEG) recordings, and examining eye movement behavior through eye-tracking (ET). Data from these methods provide us with very different but complimentary information. While behavioral data informs us about the patients' performance, the examination of ERPs and ET data allows us to record discrete changes in brain activity with a high degree of temporal resolution, without needing overt behavioral responses from participants. These recordings give us the unique opportunity to study the neural correlates of cognitive processes contributing to visual perception and memory. More recently, we have been using magnetic resonance imaging (MRI) to further understand these mechanisms in healthy and diseased aging.
Vanderbilt Memory and Alzheimer's Aging Memory
Visual perception and memory
Our recent projects have used behavioral and eye tracking methods to understand how the medial temporal lobe contributes to the intersection of visual perception and memory. Particpants who are required to make speeded perceptual decisions rely on memory and the refereshing of memory representations on a constant basis. Patients with early memory problems are just as accurate in there identification of target items, but are easily distracted by items that share certain visual features, such as color and spatial frequency. Likely due to perirhinal pathology, these patients much refresh their visual representations more often and more frequently than controls.
The role of parietal cortex in memory retrieval
The parietal cortex is of special interest, as activation is shown using numerous retrieval tasks and differing stimuli, including pictures and words. Research has also shown that parietal cortex may be one of the first areas of the brain to be affected by Alzheimer's disease. Our lab has used both ERPs and patients with parietal lesions to understand the role of parietal cortex in memory retrieval. Patients with unilateral circumscribed parietal lesions tend to show relatively unaffected memorial accuracy on tasks of item (Ally, Simons, McKeever, Peers, and Budson, 2008) and source recollection (Simons, Peers, Hwang, Ally, Fletcher, and Budson, 2008). During our work with the lesion patients, we noted that they seem to demonstrate diminshed confidence in their memory, and report that the experience less 'vividness' in their episodic memory since their lesion (typically tumor resection). This led us to speculate the perhaps the parietal lobes were involved in subjective aspects of memory. Specifically we hypothesized that the parietal old/new effect may reflect the subjective experience of recollection (Ally, Simons, et al., 2008). We recently used experimental manipulation to provide evidence for this hypothesis (McKeever, Ally, Waring, and Budson, submitted).
Vanderbilt Memory and Alzheimer's Aging Memory
Interactions between implicit and explicit memorial processes
This is a new area for the MDR Lab. It was born out of our recent finding of intact early frontal ERP activity for patients with MCI and AD (Ally, McKeever, Waring, and Budson, 2009). Despite impaired accuracy and explicit recollection, patients with MCI and AD show intact implicit memory, particularly conceptual fluency (O'Connor & Ally, 2010). A recent study showed that when stimuli were studied by patients and they performed an implicit memory task, performance was similar to healthy older adults, but when the same stimuli were studied and they were asked to take an explicit memory test, performance was significantly impaired. This is particularly relevant for visual information (Ko & Ally, 2011). We are currently using ERPs and experimental manipulation to better understand this phenomenon (Ko, Duda, Hussey, & Ally, in prep).
Structural and functional neuroimaging of visual perception and memory
In collaboration with Dr. Manus Donahue's lab at the Vanderbilt University Institute of Imaging Science, we are currently working on novel magnetic resonance imaging sequences at 3 and 7 Telsa to understand the earliest structural, hemodynamic and metabolic changes in the brain of those at high risk for Alzheimer's disease. We are currently recruiting those with a first generation relative (parent or sibling) with Alzheimer's and those that have been diagnosed with amnestic mild cognitive impairment. Our plans are also to include work from Dr. Tricia Thornton-Wells' lab focusing on how genetics may play a role in the development and expression of Alzheime'r disease. These neuroimaging and genetics data will also be used to examine possible causative roles in very early cognitive changes in the individuals with a family history.
Current Research Support
The lab is currently supported by NIH grants F32 AG044076 (PK), K23 AG031925 (BA) and R01 AG038471 (BA) from NIA and the Vanderbilt University Department of Neurology and Neurosciences Institute.