Number-Stroop performance in normal aging and Alzheimer's-type dementia

Age-related effects in magnitude and place-value processing

While general cognitive skills decline during aging, numerical skills seem to be mainly preserved. Such skills are essential for an independent life up to old age, e.g., when dealing with money or time. Operating with numbers usually requires number magnitude and place-value processing. The question is whether these processes are negatively affected by aging due to the general cognitive decline or positively affected due to lifelong experience with numbers. Therefore, we investigated age-related changes in the distance and compatibility effects in single-digit, two-digit, and four-digit number comparison. On the one hand, older adults took longer for number processing and showed a smaller distance effect, indicating altered number magnitude representations. On the other hand, older adults were better in place-value processing as indicated by a smaller compatibility effect than in younger adults. We conclude that aging differentially affects basic numerical skills.

Repetition suppression in aging: A near-infrared spectroscopy study on the size-congruity effect

Age-related changes in the hemodynamic response regarding inhibition capacity and repetition suppression were examined using a modified version of the numerical Stroop task. Young (20-38 yrs; M = 28 yrs; N = 18), middle-aged (47-59 yrs; M = 52 yrs; N = 17), and older participants (60-78 yrs; M = 69 yrs; N = 19) solved a physical and numerical version of the size-congruity task, in which trials from the same experimental condition were presented in triplets. Response times revealed a strong Stroop effect in both tasks (faster reaction times during neutral than during incongruent trials) and increased with participants' age. Reaction times decreased with item repetition. In line with previous studies, the hemodynamic response (relative concentration changes in oxygenated and deoxygenated hemoglobin) assessed with near-infrared spectroscopy was comparable across incongruent and neutral trials. Strong repetition suppression of the oxygenated hemoglobin response was observed in frontal brain regions as well as in the left parietal region in all age groups. In middle and right parietal regions, repetition suppression decreased with age and was absent among older participants. These results indicate a reduced adaptation of the hemodynamic response in middle and right parietal regions of older individuals' brains in response to repeated interference control.

Development and evaluation of a self-administered on-line test of memory and attention for middle-aged and older adults

There is a need for rapid and reliable Internet-based screening tools for cognitive assessment in middle-aged and older adults. We report the psychometric properties of an on-line tool designed to screen for cognitive deficits that require further investigation. The tool is composed of measures of memory and executive attention processes known to be sensitive to brain changes associated with aging and with cognitive disorders that become more prevalent with age. Measures included a Spatial Working Memory task, Stroop Interference task, Face-Name Association task, and Number-Letter Alternation task. Normative data were collected from 361 healthy adults age 50–79 who scored in the normal range on a standardized measure of general cognitive ability. Participants took the 20-minute on-line test on their home computers, and a subset of 288 participants repeated the test 1 week later. Analyses of the individual tasks indicated adequate internal consistency, construct validity, test-retest reliability, and alternate version reliability. As expected, scores were correlated with age. The four tasks loaded on the same principle component. Demographically-corrected z-scores from the individual tasks were combined to create an overall score, which showed good reliability and classification consistency. These results indicate the tool may be useful for identifying middle-aged and older adults with lower than expected scores who may benefit from clinical evaluation of their cognition by a health care professional.

Implications of number-space synesthesia on the automaticity of numerical processing

Number-space synesthetes visualize numbers in specific spatial configurations. Their spatial-numerical perceptions are assumed to be automatic in nature and have been found to affect performance in various numerical tasks. The current study tested whether synesthetic number-space associations can modulate the well-established Size Congruency Effect (SiCE), which is considered to be an indication for the automaticity of numerical processing. Two groups, number-space synesthetes and matched controls, were tested on a numerical Stroop task (Henik and Tzelgov, 1982). In separate blocks, participants were presented with two digits and asked to make comparative judgments regarding either numerical values (numerical comparison) or physical size (physical comparison). Both dimensions were manipulated orthogonally, creating three congruency levels: congruent (e.g., 2 7), incongruent (e.g., 2 7) and neutral (e.g., 2 2 and 2 7 for physical and numerical blocks, respectively). For the numerical block, both synesthetes and controls showed the classic SiCE, indicating similar automatic processing of physical magnitude. However, in the physical block, synesthetes showed a lack of automatic numerical magnitude processing when the numbers to be compared were presented incompatibly with their relative position on the synesthetic number-form. This finding strongly suggests that synesthetes’ number-space perceptions affect their ability to automatically process the semantic meaning of numerals. The involvement of space in automatic magnitude processing for number-space synesthetes and non-synesthetes is discussed.

Inhibition impairments in Alzheimer's disease, mild cognitive impairment and healthy aging: effect of congruency proportion in a Stroop task

The goal of this study was to assess inhibition and goal maintenance in persons with Alzheimer's disease, mild cognitive impairment, healthy older adults and younger adults. This was done by using a task that compared the Stroop effect in pure blocks, that comprised only incongruent trials, with the Stroop effect in mixed blocks, in which 25% of trials were incongruent and 75% were congruent (Kane & Engle, 2003). Those conditions were administered to 20 healthy younger and 20 older control participants, and to 20 participants meeting criteria for MCI and 11 for AD. Results show reduced resistance to interference as a consequence of healthy aging and only partially impaired goal-maintenance capacities. Interference and goal maintenance are also impaired when comparing MCI and AD to healthy older adults, with AD suffering from a more severe impairment than MCI. In addition, there is a partial preservation of goal-maintenance capacities in MCI because reducing response speed allows them to maintain a level of error rate similar to that of healthy older adults. In contrast, AD persons suffer from a complete breakdown of goal-maintenance capacities, as is suggested by deficits on both response time and error rates.

Revisiting inhibitory control across the life span: insights from the ex-Gaussian distribution

Changes in inhibitory control occur across the life span and have been associated with alterations in prefrontal function. In this study, ex-Gaussian analysis was used to reexamine data from an inhibitory control task. Participants (ages 6 to 82 years) composed three groups: children, young adults, and older adults. In fitting the ex-Gaussian distribution to reaction time data, estimates of three parameters were obtained: mu (mu), reflecting average performance; sigma (sigma), reflecting variability in performance; and tau (tau), reflecting extremes in performance. Older adults differed from young adults in terms of mu, sigma, and tau. For children, mu and tau values were comparable to those of young adults; sigma, however, was different. Thus, inhibitory changes in older adults were due to slower, more variable, and more extreme responding. Inhibitory changes in children were due only to more variable responding. These findings suggest that different mechanisms underlie age-related changes in inhibitory control during different epochs of the life span. This study demonstrates that the ex-Gaussian approach provides a finer level of analysis than data analytic approaches typically used in neuropsychological research.

Current awareness in geriatric psychiatry. Bibliography

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley &amp: Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of geriatric psychiatry. Each bibliography is divided into 9 sections: 1 Books, Reviews &amp: Symposia; 2 General; 3 Assessment; 4 Epidemiology; 5 Therapy; 6 Care; 7 Dementia; 8 Depression; 9 Psychology. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted