Frontal Recruitment During Response Inhibition in Older Adults Replicated With fMRI

Recent research has explored age-related differences in multiple areas of cognitive functioning using fMRI, PET, and SPECT. However, because these studies used different tasks, subjects, and methods, little is known about whether the results of these studies are generalizable or repeatable. The present study replicated a previous study [Psychol. Aging 17 (2002) 56] using the same Go/No-go task with a subset of 11 of the original older adult subjects, and using the same fMRI scanner and imaging methods. A direct comparison was made between these participants at Time 1 and Time 2 for both behavioral and functional data. These participants were also compared to a new young adult group of 11 participants. Although the current young adult group did not perform as well as the original young adult group, the original finding of enhanced left prefrontal activation in older adults relative to younger adults was replicated. Furthermore, when comparing Time 1 to Time 2, older adults exhibited comparable areas of activation, but significantly greater magnitude of activation at Time 1 in a few clusters. The findings indicate that older adults exhibit more bilateral brain activity during this task than young adults, which appears compensatory and is repeatable over time. The magnitude of regional activation, however, may vary with extraneuronal factors such as signal-to-noise ratio or task experience. This study adds to existing research suggesting that bilateral frontal activation is a predominant finding in the aging literature, and not specific to certain tasks in age group comparisons

Competition and market structure in local real estate markets

The persistence of the standard six percent real estate sales commission across markets and over time calls into question the competitiveness of the residential real estate brokerage industry. While there is anecdotal evidence that some local real estate markets are fairly concentrated, no systematic study of market structures has been conducted. We have collected primary data on the number and market shares of real estate brokers in a variety of small, medium, and large real estate markets across the U.S. for 2007 and 2009. In addition to these cross sectional data, we have also collected longitudinal data on the size distribution of firms for Louisville, KY for a nine-year period. In our cross-sectional analysis of medium and large markets, we find no evidence that market concentration might create problems for competition. We do find that small markets on average have higher HHI’s than medium and large markets. The longitudinal analysis reveals that many small brokers are in and out of the market, selling a house or two one year and selling zero houses the next year.HHI; real estate brokerage competition; Herfindahl-Hirschman Index

Assessing the Cell Phone Challenge to Survey Research in 2010

Updates an analysis of the complexity of including cell phone samples in surveys and issues of non-coverage bias. Examines weighted estimates from landline, cell, and combined samples; demographic and other characteristics of each group; and implications

fMRI of Healthy Older Adults During Stroop Interference

The Stroop interference effect, caused by difficulty inhibiting overlearned word reading, is often more pronounced in older adults. This has been proposed to be due to declines in inhibitory control and frontal lobe functions with aging. Initial neuroimaging studies of inhibitory control show that older adults have enhanced activation in multiple frontal areas, particularly in inferior frontal gyrus, indicative of recruitment to aid with performance of the task. The current study compared 13 younger and 13 older adults, all healthy and well educated, who completed a Stroop test during functional magnetic resonance imaging. Younger adults were more accurate across conditions, and both groups were slower and less accurate during the interference condition. The groups exhibited comparable activation regions, but older adults exhibited greater activation in numerous frontal areas, including the left inferior frontal gyrus. The results support the recruitment construct and suggest, along with previous research, that the inferior frontal gyrus is important for successful inhibition