Shawn E. Christ

Motion Onset Captures Attention

Although visual motion may seem salient, motion per se does not automatically attract attention. We show here, however, that the onset of motion does indeed attract attention. In three experiments, subjects identified target letters in displays that contained targets and distractors. There was no advantage for moving letters among static ones, but there was an advantage for objects that had recently started to move despite the fact that the motion was uninformative. If some additional time was allowed to elapse after motion onset, inhibition of return slowed responding to the item that had started to move—a further sign that the motion onset had captured attention. Finally, detection of target letters was found to be independent of the number of distractors in the display if the target had undergone motion onset, also indicative of attentional capture. We discuss the adaptive significance of sensitivity to onsets in the presence of a relative insensitivity to ongoing motion.

The Contributions of Prefrontal Cortex and Executive Control to Deception: Evidence from Activation Likelihood Estimate Meta-analyses

Previous neuroimaging studies have implicated the prefrontal cortex (PFC) and nearby brain regions in deception. This is consistent with the hypothesis that lying involves the executive control system. To date, the nature of the contribution of different aspects of executive control to deception, however, remains unclear. In the present study, we utilized an activation likelihood estimate (ALE) method of meta-analysis to quantitatively identify brain regions that are consistently more active for deceptive responses relative to truthful responses across past studies. We then contrasted the results with additional ALE maps generated for 3 different aspects of executive control: working memory, inhibitory control, and task switching. Deception-related regions in dorsolateral PFC and posterior parietal cortex were selectively associated with working memory. Additional deception regions in ventrolateral PFC, anterior insula, and anterior cingulate cortex were associated with multiple aspects of executive control. In contrast, deception-related regions in bilateral inferior parietal lobule were not associated with any of the 3 executive control constructs. Our findings support the notion that executive control processes, particularly working memory, and their associated neural substrates play an integral role in deception. This work provides a foundation for future research on the neurocognitive basis of deception.

Attention and Memory

This article is a summary of attention and memory as well as their interactions in the context of brain imaging research performed in the last two decades. Attention is introduced under a three-component framework which divides attention into three distinct components: alerting, orienting, and executive control. Memory is introduced under the three-component model: sensory memory, short-term or working memory (WM), and long-term memory (LTM). Emphasis is put on the components showing the closest interactions, such as interactions between orienting and executive control in the area of attention and between WM and LTM.

Laboratory-based and autobiographical retrieval tasks differ substantially in their neural substrates

In designing experiments to investigate retrieval of event memory, researchers choose between utilizing laboratory-based methods (in which to-be-remembered materials are presented to participants) and autobiographical approaches (in which the to-be-remembered materials are events from the participants pre-experimental life). In practice, most laboratory studies have utilized old/new recognition memory, and most autobiographical memory studies have used the Galton-Crovitz word cueing technique [Crovitz, H.F., & Schiffman, H. (1974). Frequency of episodic memories as a function of their age. Bulletin of the Psychonomic Society, 4, 517-518]. What are the implications of these methodological choices for understanding the component processes and underlying neural substrates of memory retrieval? An Activation Likelihood Estimation (ALE) meta-analysis procedure [Turkeltaub, P., Eden, G., Jones, K., & Zeffiro, TA. (2002). Meta-analysis of the functional neuroanatomy of single-word reading: Method and validation. NeuroImage, 16, 765-780] was used to construct two whole-brain statistical maps: one showing brain regions that are consistently implicated when the task utilized is old/new recognition memory and one showing regions that tend to emerge when autobiographical event memory is queried. A comparison of the two maps shows very few regions of overlap. This basic methodological choice has a profound impact on the conclusions reached regarding human memory retrieval and its neural substrates.

Executive function in early-treated phenylketonuria: Profile and underlying mechanisms

Despite early and continuous dietary intervention, individuals with early-treated phenylketonuria (PKU) experience significant neurocognitive sequelae. An area of cognitive ability that is believed to be particularly affected is executive function (EF). This paper provides a critical review of the evidence for EF impairment in early-treated PKU within the context of recent advances in neuropsychological theory and research. The most consistent findings of PKU-related EF impairment were in executive working memory and prepotent response inhibition. Surprisingly, findings on shifting ability and other more complex aspects of EF were largely equivocal. Cohort (e.g., age, phenylalanine (Phe) levels) and task (e.g., standard clinical versus experimental tasks) related differences likely contributed to the variability in findings reported by these studies. Day-to-day EF also appears to be impaired although the precise pattern of impairment remains unclear, as does the relationship between laboratory measures of EF and questionnaires assessing day-to-day EF. Similarly, whereas several studies have found a relationship between Phe levels and EF, the best predictor variable (e.g., concurrent Phe level, lifetime Phe level, Phe level variability) of current EF performance varied from study to study. Neurologic compromise related to dopamine deficiency, white matter abnormalities, and disruptions in functional connectivity likely underlies the EF impairments described in this review. In closing, this review identifies remaining unanswered questions and future avenues for research.

Inhibitory control across the life span

Findings from previous research suggest that inhibitory control improves during early childhood and declines during late adulthood. Very few researchers, however, have examined life-span changes in this ability in single studies. Within this life-span context, we investigated 1 type of inhibitory control--the ability to inhibit aprepotent response and generate an incompatible response--in individuals ranging from 6 to 82 years of age. Examination of raw reaction time data revealed a significantly larger inhibitory control effect for children and older adults than for young adults. Using proportional and z score transformations, we demonstrated that a processing speed explanation is sufficient to account for the differences in performance between children and young adults; this explanation, however, did not adequately explain the discrepancy between young and older adults. Taken together, these findings suggest that, above and beyond differences in processing speed, inhibitory control was less efficient in older adults. Our findings are consistent with the assertion that inhibitory control develops quite early and declines at the later end of the developmental spectrum.

A neural region of abstract working memory

Over 350 years ago, Descartes proposed that the neural basis of consciousness must be a brain region in which sensory inputs are combined. Using fMRI, we identified at least one such area for working memory, the limited information held in mind, described by William James as the trailing edge of consciousness. Specifically, a region in the left intraparietal sulcus was found to demonstrate load-dependent activity for either visual stimuli (colored squares) or a combination of visual and auditory stimuli (spoken letters). This result was replicated across two experiments with different participants and methods. The results suggest that this brain region, previously well known for working memory of visually presented materials, actually holds or refers to information from more than one modality.

Inhibitory Control Following Perinatal Brain Injury

Evidence from developmental, lesion, and neuroimaging studies indicates that the prefrontal cortex plays a major role in executive abilities, including inhibitory control. Proficient executive performance, however, relies not only on the integrity of the prefrontal cortex but also on its interactions with other brain regions. In the current study, the authors focused on the effect that early damage to the white matter tracts interconnecting prefrontal and other brain regions has on inhibitory control. Data were collected from 13 children with bilateral spastic cerebral palsy and from a control group of 20 children with no history of neurologic compromise. Converging evidence from 3 separate paradigms is presented that strongly suggests these children experience impairments in inhibitory control. Findings are discussed within the context of current cognitive and neuroanatomical models of inhibition.

Psychiatric Symptoms and Psychosocial Difficulties in Young Adults with Autistic Traits

A screening version of the social responsiveness scale (SRS) was administered to 1,847 university students to identify a subgroup reporting significantly greater autism traits relative to their peers (High SRS group). A group reporting minimal autism traits was also identified (Low SRS group) matched for age, gender, and attentional difficulties. We administered the Behavioral Assessment System for Children—2nd edition (BASC-2), a comprehensive questionnaire designed to assess psychiatric symptoms and personality characteristics, to both groups. The high SRS group reported significantly more difficulties across the majority of areas, including depression/anxiety, interpersonal relationships, and personal adjustment. Thus, young adults reporting a greater degree of autistic traits also reported greater psychiatric difficulties across a wide psychosocial range.

Evidence for selective inhibitory impairment in individuals with autism spectrum disorder.

OBJECTIVE The social and communicative challenges faced by individuals with autism spectrum disorder (ASD) are often compounded by additional difficulties with executive function. It remains unclear, however, to what the extent individuals with ASD experienced impairment in inhibitory control. The objective of the present study was to assess the three main subtypes of executive inhibitory control within a single ASD sample thus providing new insight into the unique ASD-related pattern of sparing and impairment observed across different aspects of inhibitory control. METHOD A sample of 28 children with ASD (mean age = 13.1 years) and a comparison group of 49 neurologically uncompromised children (mean age = 13.3 years) participated. A prepotent response inhibition task, a flanker visual filtering task, and a proactive interference memory task were used to evaluate prepotent response inhibition, resistance to distracter interference, and resistance to proactive interference, respectively. RESULTS After accounting for individual differences in noninhibition abilities (e.g., processing speed) and overall level of functioning, there was no evidence of group-related differences in inhibitory performance on the prepotent response inhibition test or proactive interference test. ASD-related impairments in inhibitory control were evident, however, on the flanker visual filtering task. CONCLUSIONS Taken together, the present findings indicate that ASD is associated with impairments in some, but not all, aspects of inhibitory control. Individuals with ASD appear to have difficulty ignoring distracting visual information, but prepotent response inhibition and resistance to proactive interference are relatively intact. The current findings also provide support for a multitype model of inhibitory control.