Inhibitory control deficits in vascular cognitive impairment revealed using the MILO task.

We used the MILO (Multi-Item Localization) task to characterise the performance of a group of older adults diagnosed with mild to moderate vascular cognitive impairment (VCI). The MILO task is designed to explore the temporal context of visual search and in addition to measuring overall completion time, provides a profile of serial reaction time (SRT) patterns across all items in a sequence. Of particular interest here, is the Vanish/Remain MILO manipulation that can identify problems with inhibitory control during search. Typically, the slope of the SRT functions are identical, regardless of whether items Vanish or Remain visible when selected, indicating an ability to ignore previously selected targets. Based on the distributed nature of VCI-related pathology and previous visual search studies from our group, we speculated that MILO performance would be compromised in this group of participants when items remained visible after being selected relative. Compared to cognitively healthy, age-matched control participants, the performance of VCI participants was characterised by overall slowing, increased error rates, and crucially, a compromised ability to use inhibitory tagging. As predicted, VCI participants had a significantly shallower Remain versus Vanish SRT function, whereas slopes were identical for control groups. Overall, our findings suggest that the MILO task could be a useful tool for identifying non-age-related changes in behaviour with patient populations, and clearly hints at a specific inhibitory deficit in VCI.

Activation, Inhibition, or Something Else: An Exploratory Study on Response Priming Using Moving Dots as Primes in Middle-Aged and Old Adults

Response priming refers to the finding that a prime stimulus preceding a target stimulus influences the response to the following target stimulus. With young subjects, using moving dot stimuli as primes indicated faster responses to compatible targets (i.e., prime and target are associated with the same response) with short stimulus onset asynchronies (SOAs). In contrast, with longer SOAs, participants responded faster to incompatible targets. In the present study, we extended the evidence by comparing middle-aged (50–65 years) and old (66–87 years) adults. With two different motion types, the result found in young participants was replicated in the middle-aged adults. In contrast, old adults showed large positive compatibility effects with the short SOA but neither activation nor inhibition effects with the longer SOA. We discuss our findings in light of several theoretical accounts (i.e., inhibitory deficit, deautomatization, evaluation window account, attention, rapid decay).

Examining theories of cognitive ageing using the false memory paradigm

Changes in memory performance with advancing age have been well documented, even in the absence of brain injury or dementia. The mechanisms underlying cognitive ageing are still a matter of debate. This article describes a comparison between young (18-25 years old) and older (60+ years) adults using the Deese–Roediger–McDermott false memory paradigm and manipulating the number of words included in the memory lists. Two key theories of cognitive ageing (the Inhibitory Deficit Hypothesis and the Transmission Deficit Hypothesis) predict opposing patterns on this task. Results showed that longer lists increase the likelihood that a lure is retrieved and that older adults are more susceptible to false memories than are younger adults. We argue that these findings are supportive of the Inhibitory Deficit Hypothesis and cannot easily be reconciled with the Transmission Deficit Hypothesis account.

The effect of aging on inhibition in task switching: Controlling for episodic retrieval

Inhibition in task switching is inferred from n–2 task repetition costs: responses areslower and less accurate to ABA task switching sequences than CBA sequences, thought to reflect the persisting inhibition of task A in an ABA sequence which hampers re-activation attempts. Despite the inhibitory deficit hypothesis of age-related decline in cognition, studies have found no consistent age-related difference in n–2 task repetition costs. Recent work has shown that extant measures of the n–2 task repetition cost are contaminated with episodic retrieval effects, which inflate estimates of inhibition. The current study revisited potential age-related differences in n–2 task repetition costs in a design that controls for episodic interference. We find equivalent n–2 task repetition costs in older and younger adults in response times, which provides converging evidence of no age-related decline of inhibition in task switching.

Does Rumination Cause “Inhibitory” Deficits?

Inhibitory processes have been implicated in depressive rumination. Inhibitory deficits may cause difficulties in disengaging from ruminative content (e.g., Joormann, 2005), or rumination may constitute a working memory load, causing deficits in inhibitory control (e.g., Hertel, 2004). These hypotheses have different implications for the treatment of depression. We conducted a systematic review of existing evidence, and conclude that most studies do not unambiguously measure inhibition. The majority of published evidence is correlational, and thus supports neither causal direction. No published experimental studies have investigated the inhibitory deficit -? rumination causal direction, and only six have investigated the rumination -? inhibitory deficit hypothesis. In two of these studies the dependent variable has low construct validity. One study reported no effect of rumination on interference, and three did not control for mood effects. There is need for carefully designed experimental research that has the potential to investigate these proposed causal mechanisms.