Stimulus probability and motor response in young and old adults: an ERP study

Developments of possible clinical diagnostic methods for parkinson's disease: event-related potentials

In this study, Event-Related Potential (ERP) analyzes were performed to detect cognitive impairments in PD with Deep Brain Stimulation (DBS). A total of 85 volunteers underwent ERP analysis and neuropsychological testing (NPT) to determine cognitive level. In ERP analyses, prolonged latencies were observed in PD groups. However, patients implanted with DBS showed a decrease in latencies, a decrease in symptoms and statistical improvements in both cognitive and attention skills. Considering all these data, ERP results are promising as a noninvasive method that can be used in both disease status and diagnosis of PD.

Activation timing of postural muscles of lower legs and prediction of postural disturbance during bilateral arm flexion in older adults

Background

Activation timings of postural muscles of lower legs and prediction of postural disturbance were investigated in young and older adults during bilateral arm flexion in a self-timing task and an oddball task with different probabilities of target presentation. Arm flexion was started from a standing posture with hands suspended 10 cm below the horizontal level in front of the body, in which postural control focused on the ankles is important.

Methods

Fourteen young and 14 older adults raised the arms in response to the target sound signal. Three task conditions were used: 15 and 45% probabilities of the target in the oddball task and self-timing. Analysis items were activation timing of postural muscles (erector spinae, biceps femoris, and gastrocnemius) with respect to the anterior deltoid (AD), and latency and amplitude of the P300 component of event-related brain potential.

Results

For young adults, all postural muscles were activated significantly earlier than AD under each condition, and time of preceding gastrocnemius activation was significantly longer in the order of the self-timing, 45 and 15% conditions. P300 latency was significantly shorter, and P300 amplitude was significantly smaller under the 45% condition than under the 15% condition. For older adults, although all postural muscles, including gastrocnemius, were activated significantly earlier than AD in the self-timing condition, only activation timing of gastrocnemius was not significantly earlier than that of AD in oddball tasks, regardless of target probability. No significant differences were found between 15 and 45% conditions in onset times of all postural muscles, and latency and amplitude of P300.

Conclusion

These results suggest that during arm movement, young adults can achieve sufficient postural preparation in proportion to the probability of target presentation in the oddball task. Older adults can achieve postural control using ankle joints in the self-timing task. However, in the oddball task, older adults experience difficulty predicting the timing of target presentation, which could be related to deteriorated cognitive function, resulting in reduced use of the ankle joints for postural control.

Age effects on the P300 potential and the corresponding fMRI BOLD-signal

Age has been reported to influence amplitude and latency of the P300 potential. Nevertheless, it is not yet fully understood which brain regions are responsible for these effects. The aim of this study was to investigate age-effects on the P300 potential and the simultaneously acquired BOLD signal of functional MRI. 32 healthy male subjects were investigated using an auditory oddball paradigm. The functional MRI data were acquired in temporal synchrony to the task. The evoked potential data were recorded during the intervals in between MR image acquisitions in order to reduce the influence of the scanner noise on the presentation of the tones and to reduce gradient artifacts. The age-effects were calculated by means of regression analyses. In addition, brain regions modulated by the task-induced amplitude variation of the P300 were identified (single trial analysis). The results indicated an age effect on the P300 amplitude. Younger subjects demonstrated increased parietal P300 amplitudes and increased BOLD responses in a network of brain regions including the anterior and posterior cingulate cortex, the insula, the temporo-parietal junction, the superior temporal gyrus, the caudate body, the amygdala and the parahippocampal gyrus. Single trial coupling of EEG and fMRI indicated that P300 amplitudes were predominantly associated with neural responses in the anterior cingulate cortex, the putamen and temporal brain areas. Taken together, the results indicate diminished neural responses in older compared to younger subjects especially in frontal, temporo-parietal and subcortical brain regions.

Age-related changes in orienting attention in time

Temporal cues guide attentional resources toward relevant points in time, resulting in optimized behavioral performance. Although deficits in aspects of attention have been documented in older adults, it remains unknown whether the critical ability to orient attention in time is affected by normal aging. To address this, younger and older adults participated in a temporally cued target-response experiment while electroencephalographic data were recorded. Three conditions (one detection and two discrimination tasks) were used to manipulate task complexity. Response times show that younger adults, but not older adults, used temporal cues to enhance performance regardless of task complexity. Similarly, alpha band activity (8-12 Hz) and the contingent negative variation preceding targets indicated that only younger adults engaged prestimulus, anticipatory neural mechanisms associated with temporal cues. Overall, these results provide novel evidence that older adults do not use temporal cues to orient attention in time and support an expectation deficit in normal aging.

Age-related multisensory enhancement in a simple audiovisual detection task

Older adults are known to gain more than younger adults from the simultaneous presentation of semantically congruent sensory stimuli. Although these findings are quite exciting, they may not solely be due to age-related differences in multisensory processing. Rather, enhanced integration may be explained by alterations associated with general cognitive slowing. This study utilized a task that eliminated most high-order cognitive processing. As such, no significant differences in unisensory response times were seen; however, older adults actually showed faster multisensory responses than younger adults. Older adults continued to show significantly greater multisensory enhancement than younger adults. Data support the conclusion that differences in multisensory processing for older adults cannot be explained solely by the effects of general cognitive slowing.

Aging, physical activity, and cognitive processing: an examination of P300

Physical activity appears to attenuate the decline of cognitive function typically observed in older men and women. The P300 component of the event-related potential (ERP) is particularly affected by aging and allows for basic neurobiological assessment of cognitive function. Three aspects of the P300 component (i.e. latency, amplitude, and area under the curve (AUC)), elicited by an oddball task, were derived to assess cognitive function in young and older participants (N=73) who were further classified as high- and low-active. The low-active elderly participants exhibited larger AUC values than those observed in all other groups which were undifferentiated. That is, the high-active elderly and the young participants exhibited smaller AUC values than the low-active older group. In conclusion, higher levels of physical activity in the elderly may be associated with a reduction in the neural resources allocated in response to simple cognitive challenge. This interpretation is consistent with the concept of psychomotor efficiency proposed by Hatfield and Hillman [The psychophysiology of sport: a mechanistic understanding of the psychology of superior performance. In: Singer RN, Hausenbias HA, Janelle CM, editors. Handbook of sport psychology. 2nd ed. New York: Wiley; 2001, p. 362-88].

An ERP study of famous face incongruity detection in middle age

Age-related changes in famous face incongruity detection were examined in middle-aged (mean = 50.6) and young (mean = 24.8) subjects. Behavioral and ERP responses were recorded while subjects, after a presentation of a "prime face" (a famous person with the eyes masked), had to decide whether the following "test face" was completed with its authentic eyes (congruent) or with other eyes (incongruent). The principal effects of advancing age were (1) behavioral difficulties in discriminating between incongruent and congruent faces; (2) a reduced N400 effect due to N400 enhancement for both congruent and incongruent faces; (3) a latency increase of both N400 and P600 components. ERPs to primes (face encoding) were not affected by aging. These results are interpreted in terms of early signs of aging.

Age-related changes in involuntary and voluntary attention as reflected in components of the event-related potential (ERP)

The present paper provides an overview of age-related changes in both involuntary and voluntary attention in adult subjects as manifested in scalp-recorded ERPs. A decline in orienting with old age was inferred from a substantial reduction with age in the magnitude of deviance-related ERP components like MMN, target as well as nontarget P3s, novelty P3 and N400. A review of focused attention studies further suggested that old and young subjects do not differ substantially in the quality of attentional operations. In old subjects early selection processes, as reflected in their selection potentials, have a somewhat slower onset than in young subjects, especially in conditions in which selection is based upon complex discrimination of stimulus features. Furthermore, the global pattern emerging from visual and memory search studies is that search-related negativities in the ERPs are smaller and of longer duration in old than in young subjects over the central and anterior scalp sites. These effects could indicate that controlled search is less intense or takes more time per search operation in old than in young subjects. At more posterior scalp sites there was tendency towards an enhanced search-related negativity that could reflect a specific difficulty (or compensatory increase in mental effort) of old subjects in spatially locating targets in complex visual fields.

The effect of motivational instructions on P300 amplitude

The aim of this investigation was to determine the effect on P300 amplitude of instructions aimed at increasing the subject's degree of task involvement. To this end, two different studies were carried out. In Study 1, 20 university students were tested with an auditory event-related potential (ERP) oddball paradigm (target: 1,100 Hz; standard: 1,000 Hz) in two consecutive runs, each with a different set of instructions; after the first run, subjects were verbally motivated to increase their level of performance in the second run. In Study 2 (performed 1 year later), ERPs were similarly obtained from the same subjects during two oddball runs, but this time both tests were preceded by neutral instructions. The amplitude and latency of N1 and P2 elicited by non-targets and of N2 and P3 in target waveforms were evaluated. The findings showed that following motivating instructions, P3 amplitude increased while P3 latency showed a non-significant decrease. The amplitude of P2 to non-target stimuli--which could be interpreted as P250--was also affected by the instructions provided. The overall results suggest that the presentation of motivating instructions is followed by a higher amount of attentional resources allocated to all stimuli, and a more efficient evaluation and discrimination of relevant targets. The implication of these findings for the clinical use of P300 has been discussed.

Learning and self-regulation of slow cortical potentials in older adults

Two groups of subjects, aged 20-28 and 50-64, respectively, matched for health status and verbal abilities, learned to control their slow cortical potentials (SCP) in a feedback paradigm by producing, on command, SCP shifts in either positive or negative direction. Both groups were able to differentiate significantly between the positivity task and the negativity task, with the differentiation score being only slightly (and not significantly) lower in older than in younger subjects. In all conditions, however, significantly more negative brain responses were obtained in older than in younger subjects. This effect was larger in the positivity task versus negativity task, and larger in trials without continuous SCP feedback versus trials with feedback. Additionally four learning tasks were carried out with all subjects. The older group demonstrated substantial performance deficits in two tasks with explicit learning (verbal and visual). In contrast, implicit learning (perceptual learning and skill acquisition) was not impaired with age. The results are at odds with the idea of general age-related learning deficit and concur with the hypothesis that only explicit, but not implicit, learning processes are compromised in older subjects. The pattern of consistently more negative SCP shifts produced by elderly subjects may indicate their impaired cortical inhibition. Another interpretation, which does not exclude the inhibitory deficit hypothesis but seems to better agree with other psychophysiological data, may be that older subjects have disturbance in the system controlling arousal and effort.

Varieties of inhibition: manifestations in cognition, event-related potentials and aging

Inhibition and facilitation are the driving forces of selective attention. Some important and still unresolved conceptual issues with respect to facilitation and inhibition are: (a) are they separate processes with different neural substrates (b) what is their time course and (c) what is their temporal locus: do they operate at the level of early sensory, central or response-related selection processes? In this introductory article we present a overview of relevant experimental paradigms that are also (in part) reflected in the contributions of this special volume, and discuss the major behavioral and psychophysiological findings from which inhibitory processes have been inferred. The global pattern of the results indicates that there are multiple inhibitory systems and processes in the central nervous system that may be expressed in many different ways. Our overview of paradigms together with the aging-related literature leads us to propose a framework for conceptualizing inhibitory processes in terms of three distinct but interacting neural systems at the level of anterior and posterior cortices and the brain stem.

The effects of sleep loss on task performance and the electroencephalogram in young and elderly subjects

The effects of 28-h sleep loss on performance, reaction time (RT) distribution functions, and spectral composition of the EEG were evaluated in three choice-RT tasks for young (N = 12, aged 18-24 years) and old (N = 12, aged 62-73 years) subjects. Manipulations of stimulus degradation, stimulus-response compatibility, and interstimulus interval variability were to affect encoding, response selection, and motor adjustment stages, respectively. In order to discriminate between independent variables that were presumed to be computational or energetical in nature, effects on EEG spectra and RT-distributions were studied. Spectra of the EEG indicated higher cortical arousal levels for the elderly than for the young. The most dramatic effect of sleep loss on performance was a marked increase in the number of omitted responses. This effect was smaller for the elderly than for the young. The results suggest that the detrimental effects of sleep loss are smaller in the elderly, which is consistent with an inverted-U relationship between arousal and performance. The age effects on the processing stages were mainly limited to response selection.

Age and Information Processing

This paper reviews our recent studies on the effects of aging on human information processing. In these studies the event-related potentials of the brain (ERPs) recorded in visual discrimination tasks were compared in younger and older groups of subjects in four experiments. We obtained a slight age-related delay of the NA component of the ERP. This component is a correlate of elementary pattern-identification processes. Obvious latency differences appeared on the anterior positivity, selection negativity, and N2b components in tasks where the target stimuli were defined by two stimulus characteristics. These components are correlates of attentional processes, i.e., the results support the view emphasizing age-related decline of the attentional processes. In the elderly the late positivity was less sensitive to stimulus probability, and in the older groups this component was more evenly distributed over the scalp. These results are considered as an indication that the structure of stimulus sequences was less efficiently represented in the older subjects.

Age, color processing and meaningfulness: an event-related potential study

The effects of aging on event-related potentials (ERPs) and reaction time (RT) performance were investigated in a task that combined color discrimination and lexical decision. The stimuli were either words or non-words, presented either in the relevant or in the irrelevant color. RT responses were required to words in the relevant color. Stimuli appeared in the relevant color elicited attention-related ERP components (anterior positivity, selection negativity and N2b). The latency values of the attention-related ERP components and the RT were longer in the older group, indicating the slowing down of attentional processes in the elderly. In the older group the late positivity to stimuli in the relevant color was absent over the posterior locations. Unlike in the older group, in the younger subjects the words appeared in the irrelevant color elicited a central negative wave in the 400 ms range. These results are considered as a capacity limitation in the elderly in processing of the stimulus characteristics beyond to the actual stimulus-response contingencies.

Aging, stimulus identification and the effect of probability: an event-related potential study

Event-related potentials (ERPs) of younger and older subjects were compared in a simple reaction time (SRT) and in two GoNogo (20% and 80% target probability) tasks. At the T5 location, the NA component (the difference between the ERPs elicited by the frequent stimuli in the GoNogo tasks on the one hand, and the ERPs in the SRT task on the other hand) emerged earlier in the younger group. The N2b was larger in the younger group, and in this group the rare stimuli of the 80% GoNogo task elicited an enlarged N2. When compared to the older group, the stimulus probability in the younger group had a larger effect on the amplitude of the late positivity. The results show age-related changes at an early stage of the information processing activity, and larger sensitivity of the orienting system in the younger subjects.

Effects of aging on event-related brain potentials (ERPs) in a visual detection task

Event-related brain potentials (ERPs) were recorded from 74 subjects (45 men) between 18 and 82 years of age in a simple visual detection task. On each trial the subject reported the location of a triangular flash of light presented briefly 20 degrees laterally to the left or right visual field or to both fields simultaneously. ERPs to targets exhibited a similar morphology including P1, N1, P2, N2, and P3 components across all age groups. The principal effects of advancing age were (1) a marked reduction in amplitude of the posterior P1 component (75-150 latency) together with an amplitude increase of an anterior positivity at the same latency; (2) an increase in amplitude of the P3 component that was most prominent over frontal scalp areas; and (3) a linear increase in P3 peak latency. These results extend the findings of age-related changes in P3 peak latency and distribution to a non-oddball task in the visual modality and raise the possibility that short-latency ERPs may index changes in visual attention in the elderly.

P300 component of the event-related potentials (ERP) during an attention task: effects of age, stimulus modality and event probability

The effects of age, stimulus modality and event probability on event-related potentials (ERP) were studied in 12 young and 12 elderly healthy subjects. The ERP were recorded from 15 electrodes referred to linked ears. Results showed that both amplitude and latency of the P300 component are affected by aging. Study of the latency of the earlier ERP components in the two age groups revealed that the P300 delay was not imputable to a delay of the earlier components. P300 amplitude and latency were also affected by event probability and stimulus modality: infrequent stimulus involved higher and later P300, but this effect was more pronounced in the young than in the old group; higher and later P300 were also recorded during the visual task compared to the auditory. Topographical repartition of the brain wave revealed a predominance of the central sites (Fz, Cz, Pz). The findings are discussed in relation to the sensitivity of the ERP assessment procedures in age related modifications of information processing.