Thus, age-related slowing in stimulus perception and motor responses would appear to account for only a small percentage of the age-related slowing of CRT latencies i.e., most of the age-related slowing in CRT latencies would appear to reflect delays in the time needed either to discriminate stimuli or to select and execute the appropriate response.Īge-related changes in visual discrimination have been examined extensively in visual search tasks ( Plude and Doussard-Roosevelt, 1989 Schialfa et al., 1998 Hommel et al., 2004). In contrast, CRT latencies, which include the additional processing stages of stimulus discrimination and response selection, slow by 90–120 ms over the same age range (see Table 1). Simple reaction time (SRT) latencies, which engage stimulus detection and response production stages, increase by 20–40 ms from age 20–65 ( Woods et al., 2015). However, age-related changes are not uniform for different processing stages. In addition, aging delays response generation in motor cortex ( Falkenstein et al., 2006 Roggeveen et al., 2007), and responses are further slowed by age-related reductions in nerve conduction velocity ( Li et al., 1998 Tobimatsu et al., 1998 Levin et al., 2011) and slowed muscle contraction ( Lewis and Brown, 1994). Aging also slows response selection due, in part, to increases in intrahemispheric ( van der Lubbe and Verleger, 2002 Rabbitt et al., 2007) and transcallosal ( Jeeves and Moes, 1996) transmission times between sensory and motor cortex. Aging has been associated with declines in alertness and attention ( Müller-Oehring et al., 2013), as well as slowed stimulus perception ( Anstey et al., 2001 Glass, 2007) and discrimination ( Madden and Allen, 1995 Schroeder et al., 1995 Yamaguchi et al., 1995). The results suggest that the age-related slowing in visual CRT latencies is largely due to delays in response selection and production.ĬRT tasks engage a number of processing stages that may be affected by aging. CRT latencies did not differ significantly in the two experiments, and similar effects of age, distractor similarity, and stimulus-response spatial compatibility were found. In Experiment 2, we replicated the findings of Experiment 1 in a second population of 178 participants (ages 18–82 years). However, the additional time needed to discriminate the more target-like distractors did not increase with age.
Participants took longer to respond to distractors with target color or shape than to distractors with no target features. Participants were faster and more accurate when the stimulus location was spatially compatible with the mouse button used for responding, and this effect increased slightly with age. Central processing time (CPT), isolated by subtracting simple reaction times (SRT) (obtained in a companion experiment performed on the same day) from CRT latencies, accounted for more than 80% of age-related CRT slowing, with most of the remaining increase in latency due to slowed motor responses. CRT latencies increased significantly with age ( r = 0.47, 2.80 ms/year). In Experiment 1, we tested 1466 participants who ranged in age from 18 to 65 years. Stimuli were presented randomly to the left and right visual fields and stimulus onset asynchronies (SOAs) were adaptively reduced following correct responses using a staircase procedure. Participants responded to a target letter (probability 40%) by pressing one mouse button, and responded to distractor letters differing either in color, shape, or both features from the target (probabilities 20% each) by pressing the other mouse button.
Here, we analyzed CRT latencies in a computerized serial visual feature-conjunction task. 5Alzheimer’s Disease Center, Department of Neurology, University of California Davis, CA, USAĪging is associated with delayed processing in choice reaction time (CRT) tasks, but the processing stages most impacted by aging have not been clearly identified.4Center for Mind and Brain, University of California Davis, CA, USA,.
3Center for Neurosciences, University of California Davis, CA, USA,.2The Department of Neurology, University of California Davis, Sacramento, CA, USA,.1Human Cognitive Neurophysiology Laboratory, Veterans Affairs Northern California Health Care System, Martinez, CA, USA,.