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everal techniques are available to investigate the brain, including x-rays such as computed tomography (CT or CAT scans), or MRI scans and functional imaging techniques such as PET scans and fMRI studies. A variety of electrophysiological analyses of brain functioning is also available including electroencephalogram (EEG) and evoked potential studies. All of these studies are informative. However, one can also perform an analysis of the thing the brain produces in copious amounts, i.e. behavior. Neuropsychology is the science that seeks to understand brain-behavior relationships.
At The New Jersey Institute for Successful Aging (NJISA), we are currently engaged in a wide variety of neuropsychological studies that are theoretical as well as applied. In human beings, the frontal lobes comprise a major portion of the total mass of the brain. It is widely recognized that the frontal lobes are a kind of ‘neural executive,’ directing activity and allocating resources. It is also well known that dementia results in damage to these critical functions of the frontal lobes.
At NJISA our research team has conducted a series of studies that seek to better understand how various types of dementing illnesses prevent the frontal lobes from doing their job. In a recently published paper (Lamar et al., Neuropsychologia), we discussed our findings that the frontal lobe functioning in patients with Alzheimer’s disease is not nearly as impaired as the frontal lobe functioning in dementia caused by subcortical vascular disease. For example, when asked to recall numbers in reverse order (called the “Digits Backwards Test”), our research group found that patients suffering from different types of dementia produce very different types of errors.
We discovered that patients with Alzheimer’s disease often make simple sequence errors. When they are asked to repeat a string of numbers such as ‘2-9-7-8-4’ in reverse order, these patients might respond with ‘4-8-2-9-7.’ On the other hand, patients with subcortical vascular dementia are often pulled to the contiguous numbers purposely positioned within the test trial and respond by saying ‘2-7-8-9-4.’ This type of error is termed a capture error. Both responses are incorrect, but the qualitative differences suggested by these various types of errors indicate that different brain structures might underlie their production. For example, members of our team have speculated that a derailed gating mechanism caused by a disruption of inputs from the thalamus, an organ located deep within the brain, into the frontal lobes may be responsible for the capture errors.
Our team attempts to use data obtained from this theoretically oriented research to better diagnose patients with suspected dementia. The effect of subcortical vascular disease on the diagnosis of dementia is controversial. In a recently published paper (“Subcortical Vascular Dementia – Integrating neuropsychological and neuroradiologic data,” Neurology 2005; 65:376 - 382), members of our group worked out an algorithm that calculates the ratio of performance on tests of memory to performance on tests of attention and concentration such as the digit backward test described above. This ratio is then applied to quantified measures of vascular disease as seen on MRI scans. In another paper, members of our team explained our finding that dementia may respond better to medicine such as Aricept when MRI scans contain evidence of at least moderate subcortical vascular disease and when the performance on tests of attention and concentration are worse as compared to tests of memory.
At the New Jersey Institute of Successful Aging, the neuropsychological information that we obtain for theoretical purposes as well as clinical purposes is quite rich, and we have found that the theoretical and the clinical are really just two sides of the same coin.
David J. Libon earned his PhD in psychology from the University of Rhode Island in 1985 and received training in clinical neuropsychology at the Boston Veterans Administration Medical Center from 1984-1985. He is the past supervising neuropsychologist at the Philadelphia Geriatric Center and past director of neuropsychology at Crozer-Chester Medical Center. Dr. Libon has been associated with the Drexel University PhD program in neuropsychology for many years. In 1998-1999, Dr. Libon served as Interim Graduate Director of the Drexel psychology program. The National Academy of Neuropsychology (NAN) recognized Dr. Libon’s research on vascular dementia by giving him the Nelson Butters Award in 1998. Currently, Dr. Libon is associate professor of psychiatry (Neuropsychology) at the New Jersey Institute for Successful Aging at UMDNJ’s School of Osteopathic Medicine in Stratford. His research interests include the brain-behavior relationships associated with executive control and working memory deficits in dementia with a special interest in vascular dementia. Dr. Libon has given presentations on what neuropsychological assessment can tell us about the brain-behavior relationships that underlie executive and working memory deficits associated with dementia syndromes such as Alzheimer’s disease, vascular dementia, and Huntington’s Disease.
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