Recent research has demonstrated that priming and recognition memory performance are not independent as traditionally thought. Evidence is accumulating suggesting that information recognized in great detail (recollected) also has higher levels of priming (Sheldon & Moscovitch, 2010; Turk-Browne, Yi, & Chun, 2006). The purpose of this dissertation was to delineate the conditions under which recognition processes (estimates of recollection and familiarity) are associated with priming, and how this changes with age. Results from a systematic crossing of level of encoding (deep versus shallow) with type of priming task (conceptual versus perceptual) suggests that the relation between priming and recognition is determined by the nature of the encoding task. Under deep encoding conditions, a greater magnitude of priming—both perceptual and conceptual—was related to subsequent recollection but only amongst younger adults. Under shallow encoding conditions, perceptual priming performance was related to subsequent familiarity in both younger and older adults. Taken together, this series of experiments suggests that the processing mode engaged during encoding dictates which processes will be engaged at retrieval (a recollection-based process, or a familiarity-based process; Henke, 2010). These findings also suggest that both recollection and familiarity have rapid and unconscious aspects that are measurable through behavioural priming tasks, aligning with a recently proposed model suggesting recollection is characterized by a two-stage process, an early, relatively automatic and unconscious stage and a later, controlled and conscious stage (Moscovitch, 2008). It is suggested that the rapid, unconscious aspects of recollection may decline across the lifespan, while the rapid, unconscious aspects of familiarity stay intact with age.

Recent research has demonstrated that priming and recognition memory performance are not independent as traditionally thought. Evidence is accumulating suggesting that information recognized in great detail (recollected) also has higher levels of priming (Sheldon & Moscovitch, 2010; Turk-Browne, Yi, & Chun, 2006). The purpose of this dissertation was to delineate the conditions under which recognition processes (estimates of recollection and familiarity) are associated with priming, and how this changes with age. Results from a systematic crossing of level of encoding (deep versus shallow) with type of priming task (conceptual versus perceptual) suggests that the relation between priming and recognition is determined by the nature of the encoding task. Under deep encoding conditions, a greater magnitude of priming—both perceptual and conceptual—was related to subsequent recollection but only amongst younger adults. Under shallow encoding conditions, perceptual priming performance was related to subsequent familiarity in both younger and older adults. Taken together, this series of experiments suggests that the processing mode engaged during encoding dictates which processes will be engaged at retrieval (a recollection-based process, or a familiarity-based process; Henke, 2010). These findings also suggest that both recollection and familiarity have rapid and unconscious aspects that are measurable through behavioural priming tasks, aligning with a recently proposed model suggesting recollection is characterized by a two-stage process, an early, relatively automatic and unconscious stage and a later, controlled and conscious stage (Moscovitch, 2008). It is suggested that the rapid, unconscious aspects of recollection may decline across the lifespan, while the rapid, unconscious aspects of familiarity stay intact with age.

Background: Cognitive impairment and cannabis use are common among patients with schizophrenia. However, the moderating role of cannabis on cognition remains unclear. Aim: We sought to examine cognition and symptomatology as a function of cannabis use patterns in schizophrenia. Methodology: Cognition was assessed in male outpatients with current cannabis dependence (n=18), historical cannabis dependence (n=21) and patients with no lifetime use (n=8). In addition, we explored the relationship between cumulative cannabis exposure and cognition among lifetime users. Results: Lifetime cannabis users demonstrated better processing speed than patients with no lifetime use. Notably, patients with current dependence exhibited robust relationships between cumulative cannabis exposure and cognition; associations were absent in former users. Conclusions: Cannabis status has minimal effects on cognition in schizophrenia. However, cumulative cannabis exposure significantly impairs cognition in current, but not former users, suggesting that the state dependent negative effects of cannabis may be reversed with sustained abstinence.

Background: Cognitive impairment and cannabis use are common among patients with schizophrenia. However, the moderating role of cannabis on cognition remains unclear. Aim: We sought to examine cognition and symptomatology as a function of cannabis use patterns in schizophrenia. Methodology: Cognition was assessed in male outpatients with current cannabis dependence (n=18), historical cannabis dependence (n=21) and patients with no lifetime use (n=8). In addition, we explored the relationship between cumulative cannabis exposure and cognition among lifetime users. Results: Lifetime cannabis users demonstrated better processing speed than patients with no lifetime use. Notably, patients with current dependence exhibited robust relationships between cumulative cannabis exposure and cognition; associations were absent in former users. Conclusions: Cannabis status has minimal effects on cognition in schizophrenia. However, cumulative cannabis exposure significantly impairs cognition in current, but not former users, suggesting that the state dependent negative effects of cannabis may be reversed with sustained abstinence.

Music training has been suggested to lead to an enhancement in the neural activity associated with music processing. It has been proposed that brain signal complexity is a reflection of the functional capacity of that neural system. The present study tested the hypothesis that musicians have a larger repertoire of brain activity associated with musical perception then nonmusicians. We used multiscale entropy to capture the complexity of the MEG signal while musicians and nonmusicians listened to different melodies. We observed that initial melody presentation elicited higher complexity in musicians compared to nonmusicians. Brain signal complexity decreased in both groups as a function of stimulus repetition. We propose that the neural networks that underlie auditory processing have a more diverse range of functioning in musicians, as compared to nonmusicians. Repetition reduces the amount of information processing and corresponding brain signal complexity.

Music training has been suggested to lead to an enhancement in the neural activity associated with music processing. It has been proposed that brain signal complexity is a reflection of the functional capacity of that neural system. The present study tested the hypothesis that musicians have a larger repertoire of brain activity associated with musical perception then nonmusicians. We used multiscale entropy to capture the complexity of the MEG signal while musicians and nonmusicians listened to different melodies. We observed that initial melody presentation elicited higher complexity in musicians compared to nonmusicians. Brain signal complexity decreased in both groups as a function of stimulus repetition. We propose that the neural networks that underlie auditory processing have a more diverse range of functioning in musicians, as compared to nonmusicians. Repetition reduces the amount of information processing and corresponding brain signal complexity.

The purpose of this thesis was to delineate the neural underpinning of three types of declarative memory retrieval; autobiographical, episodic, and semantic. Autobiographical memory was defined as the conscious recollection of personally relevant events, episodic memory as the recall of stimuli presented in the laboratory, and semantic memory as the retrieval of factual information and general knowledge about the world. Young adults participated in an event-related fMRI study in which pictorial stimuli were presented as cues for retrieval. By manipulating retrieval demands, autobiographical, episodic, or semantic memories were extracted in response to the same stimulus. The objective of the subsequent analyses was threefold: firstly, to delineate regional activations common across the memory conditions, as well as neural activations unique to each memory type (“condition-specific”); secondly, to delineate a functional network common to all three memory conditions; and, thirdly, to delineate functional network(s) of brain regions that show condition-specific activity and to assess their overlap with the common functional network. The results of the first analysis showed regional activations common to all three types of memory retrieval in the bilateral inferior frontal gyrus, left middle frontal gyrus, right caudate nucleus, bilateral thalamus, left hippocampus, and left lingual gyrus. Condition-specific activations were also delineated, including medial frontal increases for autobiographical, right middle frontal increases for episodic, and right inferior temporal increases for semantic retrieval. The second set of analyses delineated a functional network common to the three conditions that comprised 21 functionally connected neural areas. The final set of analyses further explored the functional connectivity of those brain regions that showed condition-specific activations, yielding two functional networks – one involved semantic and autobiographical conditions, and the other involved episodic and autobiographical conditions. Despite their recruiting some brain regions unique to the content of retrieved memories, the two functional networks did overlap to a degree with the common functional network. Together, these findings lend support to the notion of a common network, which is hypothesized to give rise to different types of declarative memory retrieval (i.e., autobiographical, episodic, or semantic) along a contextual continuum (i.e., highly contextualized or highly decontextualized).

There is evidence to suggest that people from different cultures have different cognitive processing styles. For example, by measuring the eye movements of American and Chinese students when viewing pictures, Chua, Boland, and Nisbett (2005) found that American students fixated more on the focal object, whereas Chinese students fixated more on the background. In a subsequent object-recognition task, the Chinese students were less likely to correctly recognize old objects presented in new backgrounds than Americans did. This study used a similar scene-viewing task to investigate whether aging modulates these cultural differences in cognitive processing style. Like Chua et al., we found that young Chinese students spent longer fixating the background than did their Western counterparts. However, we failed to replicate the accompanying memory bias observed by Chua et al. Our strongest finding was that maintaining the original background facilitated memory for objects in young participants of both cultures but not for older participants. This result suggests that older adults had poorer memory for background details and/or had poorer integration of object and background.

Perception of infant crying has been linked to the brain regions that are activated with stress and conflict monitoring, such as the anterior cingulate and amygdala. Whether the stress of cry perception affects cognitive processes is heretofore unknown. This research combines an experimental paradigm of an unsoothable infant cry task (Donovan, Leavitt, & Taylor, 2005) with a series of Rejection Stroop tasks (Dandeneau & Baldwin, 2004) with the expectation that perception of infant distress would deplete neural resources underlying the regulation of attention. Two studies were conducted on non-parent young adults and two studies were conducted on mothers of infants. Results indicated that the cry task causes negative affect and cognitive interference in non-parent young adults to a greater extent than does a musical stimulus, and that mothers of infants experience negative affect and cognitive interference comparable to the non-parent young adults.

The ability to detect a tactile stimulus during movement is markedly decreased (e.g., tactile gating), yet it is unknown whether the stimulus influences motor output. In the present study, participants moved a mechanical slider as quickly and as accurately as possible to a target. Participants received low-level electrical stimulation on the index finger of the reaching limb at various offsets relative to movement initiation. Participants reported whether they perceived the tactile cue. It was hypothesized that the detection of the stimulus would be reduced and the stimulus would influence motor output. First, a typical time course and magnitude of sensory gating was found, supporting previous observations (e.g., Chapman & Beauchamp, 2006). Second, no influence of the stimulation on motor output was observed. It was concluded that the detection of tactile cues during a goal-directed reaching task is attenuated and this stimulation does not influence motor output.