ERP and cardiovascular correlates of source memory discrimination in older and younger adults /

There is much evidence to support an age-related decline in source memory ability. However, the underlying mechanisms responsible for this decline are not well understood. The current study was carried out to determine the electrophysiological correlates of source memory discrimination in younger and older adults. Event-related potentials (ERPs) and continuous electrocardiographic (ECG) data were collected from younger (M= 21 years) and older (M= 71 years) adults during a source memory task. Older adults were more likely to make source memory errors for recently repeated, non-target words than were younger adults. Moreover, their ERP records for correct trials showed an increased amplitude in the late positive (LP) component (400-800 msec) for the most recently presented, non-target stimuli relative to the LP noted for target items. Younger adults showed an opposite pattern, with a large LP component for target items, and a much smaller LP component for the recently repeated non-target items. Computation of parasympathetic activity in the vagus nerve was performed on the ECG data (Porges, 1985). The resulting measure, vagal tone, was used as an index of physiological responsivity. The vagal tone index of physiological responsivity was negatively related to the LP amplitude for the most recently repeated, non-target words in both groups, after accounting for age effects. The ERP data support the hypothesis that the tendency to make source memory errors on the part of older adults is related to the ability to selectively control attentional processes during task performance. Furthermore, the relationship between vagal tone and ERP reactivity suggests that there is a physiological basis to the heightened reactivity measured in the LP response to recently repeated non-target items such that, under decreased physiological resources, there is an impairment in the ability to selectively inhibit bottom-up, stimulus based properties in favour of task-related goals in older adults. The inconsistency of these results with other explanatory models of source memory deficits is discussed. It is concluded that the data are consistent with a physiological reactivity model requiring inhibition of reactivity to irrelevant, but perceptually-fluent, stimuli.

Age-related changes in ERPs associated with context-based and response-based interference

Age-related differences in information processing have often been explained through deficits in older adults' ability to ignore irrelevant stimuli and suppress inappropriate responses through inhibitory control processes. Functional imaging work on young adults by Nelson and colleagues (2003) has indicated that inferior frontal and anterior cingulate cortex playa key role in resolving interference effects during a delay-to-match memory task. Specifically, inferior frontal cortex appeared to be recruited under conditions of context interference while the anterior cingulate was associated with interference resolution at the stage of response selection. Related work has shown that specific neural activities related to interference resolution are not preserved in older adults, supporting the notion of age-related declines in inhibitory control (Jonides et aI., 2000, West et aI., 2004b). In this study the time course and nature of these inhibition-related processes were investigated in young and old adults using high-density ERPs collected during a modified Sternberg task. Participants were presented with four target letters followed by a probe that either did or did not match one of the target letters held in working memory. Inhibitory processes were evoked by manipulating the nature of cognitive conflict in a particular trial. Conflict in working memory was elicited through the presentation of a probe letter in immediately previous target sets. Response-based conflict was produced by presenting a negative probe that had just been viewed as a positive probe on the previous trial. Younger adults displayed a larger orienting response (P3a and P3b) to positive probes relative to a non-target baseline. Older adults produced the orienting P3a and 3 P3b waveforms but their responses did not differentiate between target and non-target stimuli. This age-related change in response to targetness is discussed in terms of "early selection/late correction" models of cognitive ageing. Younger adults also showed a sensitivity in their N450 response to different levels of interference. Source analysis of the N450 responses to the conflict trials of younger adults indicated an initial dipole in inferior frontal cortex and a subsequent dipole in anterior cingulate cortex, suggesting that inferior prefrontal regions may recruit the anterior cingulate to exert cognitive control functions. Individual older adults did show some evidence of an N450 response to conflict; however, this response was attenuated by a co-occurring positive deflection in the N450 time window. It is suggested that this positivity may reflect a form of compensatory activity in older adults to adapt to their decline in inhibitory control.

Non-invasive measurement of trigeminal nerve somatosensory evoked potentials

Whiplash injuries are common yet enigmatic to substantiate clinically. Trigeminal somatosensory evoked potentials (TSEPs) were posited as an indicator of trigeminal nerve conduction damage resulting from whiplash. Alternating polarity square-wave current stimuli were applied transcutaneously in the facial region. 379 recorded pilot trials from 27 participants (8 male and 19 female) were utilized to develop a non-invasive recording capability for TSEPs. Stimulus intensity and artifact, cortical recording sites, stimulation electrode design and placement were explored. Statistically significant differences in amplitude of TSEP waveform components at 13, 19 and 27 ms between uninjured and whiplashed participants were noted. Increased stimulus intensity in whiplashed participants was observed to increase TSEP amplitude. The present methodology and hardware are discussed and directions for future advancement of the current process are outlined.

A framework for understanding the factors that influence spectators' recall and recognition of embedded sponsorship stimuli

Now, more than ever, sponsors of athletic events demand to see evidence of a commercial return, such as enhanced brand awareness, for their investment of cash or non-cash resources (Lough et aI., 2000). The most common way to measure the impact of perimeter signage (Le., any billboard or sign that displays a company's brand name and/or logo and which surrounds the playing area) on spectators' awareness of event sponsors has been through the use of brand name recall and recognition tests (Shilbury & Berriman, 1996). Recall testing requires spectators to list all of the sponsors they can remember seeing at, for example, an athletic event, strictly from memory and without any help (Cuneen & Hannan, 1993). With recognition testing, spectators are required to identify sponsors from a prepared list which include "dummy" brand names (i.e., sponsors that are present in the list but which do not actually sponsor the event). In order to determine whether sponsors' brand awareness objectives are being met, it is important for sport and recreation marketers to understand what influences a spectator's ability to remember (Le., recall and/or recognize) the brand names of companies who advertise on perimeter signage. The purpose this study was to examine the factors that influence spectators' recall and recognition of embedded sponsorship stimuli (i.e., company brand names on perimeter signage surrounding the play area) at a Canadian University's men's basketball game and football game. These factors included the number of games spectators attended over the course of the season (i.e., repeated exposure to sponsorship stimuli), spectators' level of involvement with the event, and spectators' level of involvement with the advertisements (i.e., perimeter signage). This study also examined the differences between recall and recognition as a means of measuring spectators' awareness of sponsors, and attempted to determine if there are sport differences in spectators' recall and recognition of perimeter signage. Upon leaving the football stadium or gymnasium, spectators were approached, at random, by trained research assistants located at each exit and asked to complete a brief survey questionnaire. Respondents completed the survey on-site. A total of 358 completed surveys were collected from spectators who attended the football (N = 277) and basketball (N = 81) games. The data suggest that football and basketball respondents recognized more sponsors' brand names than they recalled. In addition, football respondents who were highly involved with the event (i.e., those individuals who viewed attending the events as fun, interesting and exciting) attended more games over the course of the season and had significantly higher brand name recognition of sponsors who advertised on perimeter signage than those individuals with low involvement with the athletic event. Football respondents who were highly involved with the sponsors' advertisements (i.e., those individuals who viewed sponsors' perimeter signage as appealing, valuable and important) had significantly higher brand name recall of event sponsors than those individuals with low involvement with these sponsors' advertisements. Repeated exposure to perimeter signage did not have a significant influence on football or basketball respondents' recall or recognition of sponsors. Finally, the data revealed that football respondents had significantly higher recall of sponsors' brand names than basketball respondents. Conversely, basketball respondents had significantly higher recognition of sponsors' brand names than did football respondents.