Does compensatory neural activity survive old-old age?

Abstract

One mechanism that may allow older adults to continue to successfully perform certain cognitive tasks is to allocate more resources than their younger counterparts. Most prior studies have not included individuals beyond their 70s. Here, we investigated whether compensatory increases in neural activity previously observed in cognitively high performing young-old adults would continue into old-old age. Event-related potentials were recorded from 72 cognitively high performing subjects, aged 18 to 96 years old, while they participated in a subject-controlled novelty oddball paradigm in which they determined viewing duration of standard, target, and novel visual stimuli. Compared to young and middle-aged subjects, both young-old and old-old subjects exhibited an impairment of preliminary mismatch/match detection operations, indexed by an attenuated anterior N2 component. This may have placed a greater burden on the subsequent controlled decision-making process, indexed by the P3, necessitating the allocation of more resources. The relationship between age and resource allocation, as measured by P3 amplitude, from midlife to very old age (45–96 years old) followed an inverted u-shaped curve (quadratic function). It peaked between the late 60s and early 70s. Thereafter, there was an inverse relationship between age and resource appropriation. This relationship remained significant after controlling for differences in task performance and MMSE. Examining the size of the P3 component across different age groups suggests that although cognitively high performing adults in their early 80s exhibit a reduction in P3 amplitude, they have a relatively well-preserved capacity to appropriate resources. However, by the late 80s, there is a robust decline (relative to young-old adults) in the size of the P3. Our results indicate that when carrying out controlled processing linked to directing attention to salient events, cognitively high performers reach the boundary of their capacity, albeit relatively late in life. This limits their ability to appropriate additional resources as compensatory activity for age-related impairments in earlier visual processing, and suggests that such a mechanism does not tend to “survive” old-old age.

Age-related decline in differentiated neural responses to rare target versus frequent standard stimuli

“…These results add to the literature indicating that age-associated changes in indices of cerebral function may be present by middle age (Brickman et al, 2006; Gunstad et al, 2006; Park et al, 2012; Pfefferbaum et al, 2000; Riis et al, 2008; Salat et al, 2004) and continue into old-old age (Daffner et al, 2011b; Kemps & Newson, 2006; Lindenberger & Baltes, 1997; Singer, Lindenberger, & Baltes, 2003; Singer, Verhaeghen, Ghisletta, Lindenberger, & Baltes, 2003). …”

“…Otherwise, observed differences between groups could be due not to age, but to other factors (Alperin et al, 2013; Daffner et al, 2011b; Daselaar & Cabeza, 2005; Riis et al, 2008). Because there is strong evidence that selective attention reflects top-down control mechanisms (de Fockert, Rees, Frith, & Lavie, 2001; Gazzaley et al, 2008; Rissman, Gazzaley, & D'Esposito, 2009; Zanto, Rubens, Thangavel, & Gazzaley, 2011), age groups were matched in terms of executive capacity.…”

“…We hypothesized that an age-related decline in differentiated neural responses would become significant by young-old age and would progress through old-old age (Daffner et al, 2011b). The extent to which middle-aged subjects would exhibit differences in processing relative to young subjects was unclear.…”

Compensation through Increased Functional Connectivity: Neural Correlates of Inhibition in Old and Young

“…It is important to note that studies of aging often have treated the elderly as a homogeneous group, assuming the same general pattern of cognitive decline in all individuals (for exceptions, see Daffner et al, 2011;Nagel et al, 2009;Duverne, Motamedinia, & Rugg, 2008;Colcombe, Kramer, Erickson, & Scalf, 2005). However, large individual differences have been observed within the elderly population (Park & Reuter-Lorenz, 2009).…”

The Dissociation between Early and Late Selection in Older Adults

“…If not, observed differences between groups may be due to factors other than age (Daffner et al, 2011b; Daselaar & Cabeza, 2005; Haring et al, 2013; Riis et al, 2008). Most studies have not explicitly addressed this challenge.…”