Increased Early Processing of Task-Irrelevant Auditory Stimuli in Older Adults

Abstract

The inhibitory deficit hypothesis of cognitive aging posits that older adults’ inability to adequately suppress processing of irrelevant information is a major source of cognitive decline. Prior research has demonstrated that in response to task-irrelevant auditory stimuli there is an age-associated increase in the amplitude of the N1 wave, an ERP marker of early perceptual processing. Here, we tested predictions derived from the inhibitory deficit hypothesis that the age-related increase in N1 would be 1) observed under an auditory-ignore, but not auditory-attend condition, 2) attenuated in individuals with high executive capacity (EC), and 3) augmented by increasing cognitive load of the primary visual task. ERPs were measured in 114 well-matched young, middle-aged, young-old, and old-old adults, designated as having high or average EC based on neuropsychological testing. Under the auditory-ignore (visual-attend) task, participants ignored auditory stimuli and responded to rare target letters under low and high load. Under the auditory-attend task, participants ignored visual stimuli and responded to rare target tones. Results confirmed an age-associated increase in N1 amplitude to auditory stimuli under the auditory-ignore but not auditory-attend task. Contrary to predictions, EC did not modulate the N1 response. The load effect was the opposite of expectation: the N1 to task-irrelevant auditory events was smaller under high load. Finally, older adults did not simply fail to suppress the N1 to auditory stimuli in the task-irrelevant modality; they generated a larger response than to identical stimuli in the task-relevant modality. In summary, several of the study’s findings do not fit the inhibitory-deficit hypothesis of cognitive aging, which may need to be refined or supplemented by alternative accounts.

Event-Related Potentials to Changes in Sound Intensity Demonstrate Alterations in Brain Function Related to Depression and Aging

“…In contrast, we found that older adults had increased N1 responses to both repeated sounds and rare high-intensity sounds. Similarly, one previous study found an age-related increase in N1 amplitude for both repeated sounds and novel sounds (Tusch et al, 2016). The authors suggest that the increase in these responses could reflect an adaptive response to compensate for reduced processing speed in older adults.…”

“…For N1 sensory gating, responses to both standard and deviant sounds (see also Anderer et al, 1998;Tusch et al, 2016;Strömmer et al, 2017) for the conditions (increment and decrement) were included. For standard sounds, only responses to pre-deviant standards were included in the analysis because they had been repeated at least twice and therefore enabled an examination of the neural suppression related to stimulus repetition.…”

Task-Irrelevant Novel Sounds have Antithetical Effects on Visual Target Processing in Young and Old Adults

“…The impact of primary task load on the P3a to novel auditory events also is uncertain. Our work (Simon et al, 2016 ; Tusch et al, 2016a ) and that of others (SanMiguel et al, 2010a ; Sörqvist and Marsh, 2015 ; Sörqvist et al, 2016 ) lead to the prediction that higher primary task difficulty protects against distraction by increasing focal-task engagement, which would result in a smaller novelty P3a under the high load for both age groups. Finding such a result would pose a challenge to the load theory of attention (Lavie et al, 2004 ; Lavie and De Fockert, 2005 ), which posits that carrying out a more demanding primary task results in enhanced competition for the pool of limited executive control resources.…”

“…One hypothesized consequence of the aging process is increased susceptibility to distraction by irrelevant stimuli (Friedman et al, 1998 ; Andrés et al, 2006 ; Parmentier and Andrés, 2010 ). In the laboratory setting it has been shown that older individuals demonstrate enhanced early processing of irrelevant auditory stimuli during a visual oddball task (Tusch et al, 2016a ), and are more susceptible to distraction when performing working memory (Gazzaley et al, 2008 ; de Fockert et al, 2009 ), and reading-with-distraction tasks (Carlson et al, 1995 ; Li et al, 1998 ).…”

“…While low load was consistent across subjects (one target stimulus), high load was individually tailored during a pre-task assessment resulting in a similar level of performance accuracy across participants. This approach aimed to reduce the confound between age- and performance-related effects on indices of underlying information processing (Riis et al, 2008 ; Haring et al, 2013 ; Tusch et al, 2016a ).…”