A common finding in the aging literature is that of the brain's decreased within‐ and increas... more A common finding in the aging literature is that of the brain's decreased within‐ and increased between‐network functional connectivity. However, it remains unclear what is causing this shift in network organization with age. Given the essential role of the ascending arousal system (ARAS) in cortical activation and previous findings of disrupted ARAS functioning with age, it is possible that age differences in ARAS functioning contribute to disrupted cortical connectivity. We test this possibility here using resting state fMRI data from over 500 individuals across the lifespan from the Cambridge Center for Aging and Neuroscience (Cam‐CAN) population‐based cohort. Our results show that ARAS‐cortical connectivity declines with age and, consistent with our expectations, significantly mediates some age‐related differences in connectivity within and between association networks (specifically, within the default mode and between the default mode and salience networks). Additionally, connectivity between the ARAS and association networks predicted cognitive performance across several tasks over and above the effects of age and connectivity within the cortical networks themselves. These findings suggest that age differences in cortical connectivity may be driven, at least in part, by altered arousal signals from the brainstem and that ARAS–cortical connectivity relates to cognitive performance with age.
Recent work suggests that while voluntary episodic memory declines with age, involuntary episodic... more Recent work suggests that while voluntary episodic memory declines with age, involuntary episodic memory, which comes to mind spontaneously without intention, remains relatively intact. However, the neurophysiology underlying these differences has yet to be established. The current study used electroencephalography (EEG) to investigate voluntary and involuntary retrieval in older and younger adults. Participants first encoded sounds, half of which were paired with pictures, the other half unpaired. EEG was then recorded as they listened to the sounds, with participants in the involuntary group performing a sound localization cover task, and those in the voluntary group additionally attempting to recall the associated pictures. Participants later reported which sounds brought the paired picture to mind during the localization task. Reaction times on the localization task were slower for voluntary than involuntary retrieval and for paired than unpaired sounds, possibly reflecting increased attentional demands of voluntary retrieval and interference from reactivation of the associated pictures respectively. For the EEG analyses, young adults showed greater alpha event-related desynchronization (ERD) during voluntary than involuntary retrieval at frontal and occipital sites, while older adults showed pronounced alpha ERD regardless of intention. Additionally, older adults showed greater ERD for paired than unpaired sounds at occipital sites, likely reflecting visual reactivation of the associated pictures. Young adults did not show this alpha ERD memory effect. Taken together, these data suggest that involuntary memory is largely preserved with age, but this may be due to older adults' greater recruitment of top-down control even when demand for such control is limited.
There is mixed evidence on the impact of delay task difficulty on prospective memory (PM) perform... more There is mixed evidence on the impact of delay task difficulty on prospective memory (PM) performance and little research has examined this among older adults. The present study examined younger (N = 60) and older (N = 57) adults' prospective memory (PM) performance after completing an easy or difficult Raven's matrices task. To assess whether delay difficulty impacted how often participants thought about their PM intention, participants were asked to report on what they thought about during the delay task itself and retrospectively after all tasks were completed. Younger adults outperformed older adults on the PM task; however, delay task difficulty had no impact PM for either age group. Reports of thinking about the intention during the delay task differed by age group depending whether they were online or retrospective, however, overall greater reports of thinking about the intention was positively associated with PM performance.
Physical activity has positive effects on brain health and cognitive function throughout the life... more Physical activity has positive effects on brain health and cognitive function throughout the life span. Thus far, few studies have examined the effects of physical activity on white matter microstructure and psychomotor speed within the same, population-based sample (critical if conclusions are to extend to the wider population). Here, using diffusion tensor imaging and a simple reaction time task within a relatively large population-derived sample (N = 399; 18-87 years) from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN), we demonstrate that physical activity mediates the effect of age on white matter integrity, measured with fractional anisotropy. Higher self-reported daily physical activity was associated with greater preservation of white matter in several frontal tracts, including the genu of corpus callosum, uncinate fasciculus, external capsule, and anterior limb of the internal capsule. We also show that the age-related slowing is mediated by white matter integrity in the genu. Our findings contribute to a growing body of work, suggesting that a physically active lifestyle may protect against agerelated structural disconnection and slowing.
While a long history of neuropsychological research places language function within a primarily l... more While a long history of neuropsychological research places language function within a primarily left-lateralized frontotemporal system, recent neuroimaging work has extended this language network to include a number of regions traditionally thought of as 'domain-general'. These include dorsal frontal, parietal, and medial temporal lobe regions known to underpin cognitive functions such as attention and memory. In this paper, we argue that these domain-general systems are not required for language processing and are instead an artefact of the tasks typically used to study language. Recent work from our lab shows that when syntactic processing - arguably the only domain-specific language function - is measured in a task-free, naturalistic manner, only the left-lateralized frontotemporal syntax system and auditory network are activated. When syntax is measured within the context of a task, several other domain-general networks come online and are functionally connected to the f...
We were pleased to see that our opinion paper generated so many thoughtful comments, and while th... more We were pleased to see that our opinion paper generated so many thoughtful comments, and while there was some disagreement as to the role resting state data should play going forward, there was also much agreement. In reply, we briefly touch on some of the keys issues brought up by the authors and reiterate our view that task-based studies offer a greater opportunity to advance the field. Our original paper questioned the utility of the resting state approach for neurocognitive aging, but Davis, Stanley, Moscovitch, and Cabeza (2016) extended this criticism to the entire field of cognitive neuroscience, the goal of which is to "understand the neural mechanisms of cognition" (p. 1). They point out that resting state networks are commonly assumed to determine or constrain "cognitive function networks" (or networks active during cognitive tasks) and outline a number of problems with this assumption. Mainly, resting state networks are similar to, but not quite the same as, cognitive function networks because regions dynamically shift alliances in response to cognitive demands and as such, the same region can contribute to a number of different cognitive processes. Extending this notion of "process specific alliances" to aging, we know that age affects some cognitive functions and not others; and indeed, it may affect some regions and not others. But more complex still, age may affect some process specific alliances, but not others. This question can only be addressed through cross-task comparisons. For instance, we recently showed that older adults underactivate the frontoparietal network (FPN) when it works in conjunction with other attentional control and visual networks during a fluid intelligence task (an ability that declines with age), but not when the FPN works in conjunction with the frontotemporal network during language comprehension (an ability that is preserved with age; Samu, Campbell, Tsvetanov, Shafto, Cam-CAN, & Tyler, submitted for publication).
Recent years have seen the rise in popularity of the resting-state approach to neurocognitive age... more Recent years have seen the rise in popularity of the resting-state approach to neurocognitive ageing, with many studies examining age differences in functional connectivity at rest and relating these differences to cognitive performance outside the scanner. There are many advantages to the resting state that likely contribute to its popularity and indeed, many insights have been gained from this work. However, there are also several limitations of the resting-state approach that restrict its ability to contribute to the study of neurocognitive ageing. In this opinion piece, we consider some of those limitations and argue that task-based studies are still essential to developing a mechanistic understanding of how age affects the brain in a cognitively relevant mannera fundamental goal of neuroscientific research into ageing.
Remembering the past and imagining the future both involve the retrieval of details stored in epi... more Remembering the past and imagining the future both involve the retrieval of details stored in episodic memory and rely on the same core network of brain regions. Given these parallels, one might expect similar component processes to be involved in remembering and imagining. While a strong case can be made for the role of inhibition in memory retrieval, few studies have examined whether inhibition is also necessary for future imagining and results to-date have been mixed. In the current study, we test whether related concepts are inhibited during future imagining using a modified priming approach. Participants first generated a list of familiar places and for each place, the people they most strongly associate with it. A week later, participants imagined future events involving recombinations of people and places, immediately followed by a speeded response task in which participants made familiarity decisions about people's names. Across two experiments, our results suggest that ...
Healthy ageing has disparate effects on different cognitive domains. The neural basis of these di... more Healthy ageing has disparate effects on different cognitive domains. The neural basis of these differences, however, is largely unknown. We investigated this question by using Independent Components Analysis to obtain functional brain components from 98 healthy participants aged 23-87 years from the population-based Cam-CAN cohort. Participants performed two cognitive tasks that show age-related decrease (fluid intelligence and object naming) and a syntactic comprehension task that shows age-related preservation. We report that activation of task-positive neural components predicts inter-individual differences in performance in each task across the adult lifespan. Furthermore, only the two tasks that show performance declines with age show age-related decreases in task-positive activation of neural components and decreasing default mode (DM) suppression. Our results suggest that distributed, multi-component brain responsivity supports cognition across the adult lifespan, and the mai...
Slowing is a common feature of ageing, yet a direct relationship between neural slowing and brain... more Slowing is a common feature of ageing, yet a direct relationship between neural slowing and brain atrophy is yet to be established in healthy humans. We combine magnetoencephalographic (MEG) measures of neural processing speed with magnetic resonance imaging (MRI) measures of white- and gray-matter in a large (N=617, 18-88yrs), population-derived cohort (www.cam-can.org) to investigate the relationship between age-related structural differences and VEF and AEF delay across two different tasks. Using a novel technique, we show that VEFs exhibit a constant delay, whereas AEPs exhibit delay that accumulates over time. Visual delay is mediated by white-matter microstructure in the optic radiation, presumably reflecting increased transmission time, whereas auditory delay is mediated by gray-matter differences in auditory cortex, presumably reflecting less efficient local processing. Our results demonstrate that age has dissociable effects on neural processing speed, and that these effect...
Much is known about how age affects the brain during tightly controlled, though largely contrived... more Much is known about how age affects the brain during tightly controlled, though largely contrived, experiments, but do these effects extrapolate to everyday life? Naturalistic stimuli, such as movies, closely mimic the real world and provide a window onto the brain's ability to respond in a timely and measured fashion to complex, everyday events. Young adults respond to these stimuli in a highly synchronized fashion, but it remains to be seen how age affects neural responsiveness during naturalistic viewing. To this end, we scanned a large (N ¼ 218), population-based sample from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) during movie-watching. Intersubject synchronization declined with age, such that older adults' response to the movie was more idiosyncratic. This decreased synchrony related to cognitive measures sensitive to attentional control. Our findings suggest that neural responsivity changes with age, which likely has important implications for real-world event comprehension and memory.
A common finding in the aging literature is that of the brain's decreased within‐ and increas... more A common finding in the aging literature is that of the brain's decreased within‐ and increased between‐network functional connectivity. However, it remains unclear what is causing this shift in network organization with age. Given the essential role of the ascending arousal system (ARAS) in cortical activation and previous findings of disrupted ARAS functioning with age, it is possible that age differences in ARAS functioning contribute to disrupted cortical connectivity. We test this possibility here using resting state fMRI data from over 500 individuals across the lifespan from the Cambridge Center for Aging and Neuroscience (Cam‐CAN) population‐based cohort. Our results show that ARAS‐cortical connectivity declines with age and, consistent with our expectations, significantly mediates some age‐related differences in connectivity within and between association networks (specifically, within the default mode and between the default mode and salience networks). Additionally, connectivity between the ARAS and association networks predicted cognitive performance across several tasks over and above the effects of age and connectivity within the cortical networks themselves. These findings suggest that age differences in cortical connectivity may be driven, at least in part, by altered arousal signals from the brainstem and that ARAS–cortical connectivity relates to cognitive performance with age.
Recent work suggests that while voluntary episodic memory declines with age, involuntary episodic... more Recent work suggests that while voluntary episodic memory declines with age, involuntary episodic memory, which comes to mind spontaneously without intention, remains relatively intact. However, the neurophysiology underlying these differences has yet to be established. The current study used electroencephalography (EEG) to investigate voluntary and involuntary retrieval in older and younger adults. Participants first encoded sounds, half of which were paired with pictures, the other half unpaired. EEG was then recorded as they listened to the sounds, with participants in the involuntary group performing a sound localization cover task, and those in the voluntary group additionally attempting to recall the associated pictures. Participants later reported which sounds brought the paired picture to mind during the localization task. Reaction times on the localization task were slower for voluntary than involuntary retrieval and for paired than unpaired sounds, possibly reflecting increased attentional demands of voluntary retrieval and interference from reactivation of the associated pictures respectively. For the EEG analyses, young adults showed greater alpha event-related desynchronization (ERD) during voluntary than involuntary retrieval at frontal and occipital sites, while older adults showed pronounced alpha ERD regardless of intention. Additionally, older adults showed greater ERD for paired than unpaired sounds at occipital sites, likely reflecting visual reactivation of the associated pictures. Young adults did not show this alpha ERD memory effect. Taken together, these data suggest that involuntary memory is largely preserved with age, but this may be due to older adults' greater recruitment of top-down control even when demand for such control is limited.
There is mixed evidence on the impact of delay task difficulty on prospective memory (PM) perform... more There is mixed evidence on the impact of delay task difficulty on prospective memory (PM) performance and little research has examined this among older adults. The present study examined younger (N = 60) and older (N = 57) adults' prospective memory (PM) performance after completing an easy or difficult Raven's matrices task. To assess whether delay difficulty impacted how often participants thought about their PM intention, participants were asked to report on what they thought about during the delay task itself and retrospectively after all tasks were completed. Younger adults outperformed older adults on the PM task; however, delay task difficulty had no impact PM for either age group. Reports of thinking about the intention during the delay task differed by age group depending whether they were online or retrospective, however, overall greater reports of thinking about the intention was positively associated with PM performance.
Physical activity has positive effects on brain health and cognitive function throughout the life... more Physical activity has positive effects on brain health and cognitive function throughout the life span. Thus far, few studies have examined the effects of physical activity on white matter microstructure and psychomotor speed within the same, population-based sample (critical if conclusions are to extend to the wider population). Here, using diffusion tensor imaging and a simple reaction time task within a relatively large population-derived sample (N = 399; 18-87 years) from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN), we demonstrate that physical activity mediates the effect of age on white matter integrity, measured with fractional anisotropy. Higher self-reported daily physical activity was associated with greater preservation of white matter in several frontal tracts, including the genu of corpus callosum, uncinate fasciculus, external capsule, and anterior limb of the internal capsule. We also show that the age-related slowing is mediated by white matter integrity in the genu. Our findings contribute to a growing body of work, suggesting that a physically active lifestyle may protect against agerelated structural disconnection and slowing.
While a long history of neuropsychological research places language function within a primarily l... more While a long history of neuropsychological research places language function within a primarily left-lateralized frontotemporal system, recent neuroimaging work has extended this language network to include a number of regions traditionally thought of as 'domain-general'. These include dorsal frontal, parietal, and medial temporal lobe regions known to underpin cognitive functions such as attention and memory. In this paper, we argue that these domain-general systems are not required for language processing and are instead an artefact of the tasks typically used to study language. Recent work from our lab shows that when syntactic processing - arguably the only domain-specific language function - is measured in a task-free, naturalistic manner, only the left-lateralized frontotemporal syntax system and auditory network are activated. When syntax is measured within the context of a task, several other domain-general networks come online and are functionally connected to the f...
We were pleased to see that our opinion paper generated so many thoughtful comments, and while th... more We were pleased to see that our opinion paper generated so many thoughtful comments, and while there was some disagreement as to the role resting state data should play going forward, there was also much agreement. In reply, we briefly touch on some of the keys issues brought up by the authors and reiterate our view that task-based studies offer a greater opportunity to advance the field. Our original paper questioned the utility of the resting state approach for neurocognitive aging, but Davis, Stanley, Moscovitch, and Cabeza (2016) extended this criticism to the entire field of cognitive neuroscience, the goal of which is to "understand the neural mechanisms of cognition" (p. 1). They point out that resting state networks are commonly assumed to determine or constrain "cognitive function networks" (or networks active during cognitive tasks) and outline a number of problems with this assumption. Mainly, resting state networks are similar to, but not quite the same as, cognitive function networks because regions dynamically shift alliances in response to cognitive demands and as such, the same region can contribute to a number of different cognitive processes. Extending this notion of "process specific alliances" to aging, we know that age affects some cognitive functions and not others; and indeed, it may affect some regions and not others. But more complex still, age may affect some process specific alliances, but not others. This question can only be addressed through cross-task comparisons. For instance, we recently showed that older adults underactivate the frontoparietal network (FPN) when it works in conjunction with other attentional control and visual networks during a fluid intelligence task (an ability that declines with age), but not when the FPN works in conjunction with the frontotemporal network during language comprehension (an ability that is preserved with age; Samu, Campbell, Tsvetanov, Shafto, Cam-CAN, & Tyler, submitted for publication).
Recent years have seen the rise in popularity of the resting-state approach to neurocognitive age... more Recent years have seen the rise in popularity of the resting-state approach to neurocognitive ageing, with many studies examining age differences in functional connectivity at rest and relating these differences to cognitive performance outside the scanner. There are many advantages to the resting state that likely contribute to its popularity and indeed, many insights have been gained from this work. However, there are also several limitations of the resting-state approach that restrict its ability to contribute to the study of neurocognitive ageing. In this opinion piece, we consider some of those limitations and argue that task-based studies are still essential to developing a mechanistic understanding of how age affects the brain in a cognitively relevant mannera fundamental goal of neuroscientific research into ageing.
Remembering the past and imagining the future both involve the retrieval of details stored in epi... more Remembering the past and imagining the future both involve the retrieval of details stored in episodic memory and rely on the same core network of brain regions. Given these parallels, one might expect similar component processes to be involved in remembering and imagining. While a strong case can be made for the role of inhibition in memory retrieval, few studies have examined whether inhibition is also necessary for future imagining and results to-date have been mixed. In the current study, we test whether related concepts are inhibited during future imagining using a modified priming approach. Participants first generated a list of familiar places and for each place, the people they most strongly associate with it. A week later, participants imagined future events involving recombinations of people and places, immediately followed by a speeded response task in which participants made familiarity decisions about people's names. Across two experiments, our results suggest that ...
Healthy ageing has disparate effects on different cognitive domains. The neural basis of these di... more Healthy ageing has disparate effects on different cognitive domains. The neural basis of these differences, however, is largely unknown. We investigated this question by using Independent Components Analysis to obtain functional brain components from 98 healthy participants aged 23-87 years from the population-based Cam-CAN cohort. Participants performed two cognitive tasks that show age-related decrease (fluid intelligence and object naming) and a syntactic comprehension task that shows age-related preservation. We report that activation of task-positive neural components predicts inter-individual differences in performance in each task across the adult lifespan. Furthermore, only the two tasks that show performance declines with age show age-related decreases in task-positive activation of neural components and decreasing default mode (DM) suppression. Our results suggest that distributed, multi-component brain responsivity supports cognition across the adult lifespan, and the mai...
Slowing is a common feature of ageing, yet a direct relationship between neural slowing and brain... more Slowing is a common feature of ageing, yet a direct relationship between neural slowing and brain atrophy is yet to be established in healthy humans. We combine magnetoencephalographic (MEG) measures of neural processing speed with magnetic resonance imaging (MRI) measures of white- and gray-matter in a large (N=617, 18-88yrs), population-derived cohort (www.cam-can.org) to investigate the relationship between age-related structural differences and VEF and AEF delay across two different tasks. Using a novel technique, we show that VEFs exhibit a constant delay, whereas AEPs exhibit delay that accumulates over time. Visual delay is mediated by white-matter microstructure in the optic radiation, presumably reflecting increased transmission time, whereas auditory delay is mediated by gray-matter differences in auditory cortex, presumably reflecting less efficient local processing. Our results demonstrate that age has dissociable effects on neural processing speed, and that these effect...
Much is known about how age affects the brain during tightly controlled, though largely contrived... more Much is known about how age affects the brain during tightly controlled, though largely contrived, experiments, but do these effects extrapolate to everyday life? Naturalistic stimuli, such as movies, closely mimic the real world and provide a window onto the brain's ability to respond in a timely and measured fashion to complex, everyday events. Young adults respond to these stimuli in a highly synchronized fashion, but it remains to be seen how age affects neural responsiveness during naturalistic viewing. To this end, we scanned a large (N ¼ 218), population-based sample from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) during movie-watching. Intersubject synchronization declined with age, such that older adults' response to the movie was more idiosyncratic. This decreased synchrony related to cognitive measures sensitive to attentional control. Our findings suggest that neural responsivity changes with age, which likely has important implications for real-world event comprehension and memory.
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