A neuropsychological approach to differentiating cannabis-induced and primary psychotic disorders.

AIM: Rates of cannabis use are elevated in early psychosis populations, rendering it difficult to determine if an episode of psychosis is related to cannabis use (e.g., cannabis-induced psychosis), or if substance use is co-occurring with a primary psychotic disorder (e.g., schizophrenia). Clinical presentations of these disorders are often indistinguishable, hindering assessment and treatment. Despite substantial research identifying cognitive deficits, eye movement abnormalities and speech impairment associated with primary psychotic disorders, these neuropsychological features have not been explored as targets for diagnostic differentiation in early psychosis. METHODS: Eighteen participants with cannabis-induced psychosis (Mage  = 21.9, SDage  = 4.25, 14 male) and 19 participants with primary psychosis (Mage  = 29.2, SDage  = 7.65, 17 male) were recruited from early intervention programs. Diagnoses were ascertained by primary treatment teams after a minimum of 6 months in the program. Participants completed tasks assessing cognitive performance, saccadic eye movements and speech. Clinical symptoms, trauma, substance use, premorbid functioning and illness insight were also assessed. RESULTS: Relative to individuals with primary psychosis, individuals with cannabis-induced psychosis demonstrated significantly better performance on the pro-saccade task, faster RT on pro- and anti-saccade tasks, better premorbid adjustment, and a higher degree of insight into their illness. There were no significant differences between groups on psychiatric symptoms, premorbid intellectual functioning, or problems related to cannabis use. CONCLUSIONS: In early stages of illness, reliance on traditional diagnostic tools or clinical interviews may be insufficient to distinguish between cannabis-induced and primary psychosis. Future research should continue to explore neuropsychological differences between these diagnoses to improve diagnostic accuracy.

Remembering more than you can say: Re-examining "amnesia" of attended attributes.

Attribute amnesia (AA) describes a phenomenon whereby observers fail a surprise memory test which asks them to report an attribute they had just attended and used to fulfil a task goal. This finding has cast doubt on the prominent theory that attention results in encoding into working memory (WM), to which two competing explanations have been proposed: (1) task demands dictate whether attended information is encoded into WM, and (2) attended information is encoded in a weak state that does not survive the demands of the surprise memory test. To address this debate our study circumvented the limitations of a surprise memory test by embedding a second search task within a typical color-based AA search task. The search task was modified so that the attended attribute would reappear in the second search as either the target, a distractor, or not at all. Critically, our results support encoding of the attended attribute in WM though to a weaker extent than the attribute that is required for report. A second experiment confirmed that WM encoding only occurs for the attended attribute, though distractor attributes produce a bias consistent with negative priming. Our data provide novel support for a theory of memory consolidation that links the strength of a memory's representation with expectations for how it will be used in a task. Implications for the utility of this procedure in future investigations previously limited by single trial data (i.e., surprise question methodology) are discussed.

Attention bias modification in depression: A randomized trial using a novel, reward-based, eye-tracking approach.

BACKGROUND AND OBJECTIVES: Biased attention to negative information is a mechanism for risk and relapse in depression. Attentional bias modification (ABM) paradigms manipulate attention away from negative information to reduce this bias. ABM results have been mixed due to inconsistent methodologies and stimuli design. This randomized controlled trial used a novel approach to modifying attentional bias. METHODS: An eye tracker manipulated stimuli in response to participants' fixations to preferentially reward attention to positive stimuli by obscuring or enhancing image quality of negative and positive stimuli, respectively. Participants with major depressive disorder completed three 35-min sessions of active (n = 20) or sham (n = 20) ABM training. Attentional bias, memory for emotional words, and mood were assessed pre- and post-training. RESULTS: Training reduced negative attentional bias; relative to sham, active training participants focused significantly more on positive compared to negative stimuli in a free-viewing eye-tracker task (p = .038, ηp2 = 0.109) and, at trend, disengaged from sad information more quickly in a computerized task (p = .052, ηp2 = 0.096). Active training participants remembered more happy than sad words in an emotional word learning task, indicating a distal transfer of training to emotional memory (p = .036, ηp2 = 0.11). Training did not significantly affect mood in the one-week trial. LIMITATIONS: Future studies should build on this proof-of-principle study with larger sample sizes and more intensive treatment to explore which mechanisms of training may lead to improvements in mood. CONCLUSIONS: Attention biases in depression are modifiable through reward-based, eye-tracking training. These data suggest generalizability of training to other cognitive faculties - recall for affective information.

In support of selective rehearsal: Double-item presentation in item-method directed forgetting.

Despite the substantial evidence highlighting the role of selective rehearsal in item-method directed forgetting, recent work has suggested that forgetting may occur as a function of an active inhibitory mechanism that is more effortful than elaborative rehearsal processes. In the present work, we test this hypothesis by implementing a double-item presentation within the item-method directed forgetting paradigm. Participants studied two unrelated items at a time. Some words were followed by the same cue, and participants were instructed to remember or forget both items (pure condition). On other trials, participants were to remember one but forget the other word (mixed condition). Selective rehearsal and inhibition accounts make distinct predictions regarding memory performance in the double-item presentation. In Experiment 1, we compared recognition performance in the pure and mixed conditions, while in Experiment 2, we included a neutral baseline condition to further distinguish between the selective rehearsal and inhibition accounts. Contrary to the inhibition account but consistent with selective rehearsal, we found for both remember and forget items that recognition was greater in the mixed than in the pure condition. Recognition for forget items also did not differ from neutral items. We conclude that selective rehearsal, not inhibition, is responsible for item-method directed forgetting.

Temporal trimming: Evidence that common-onset masking shortens perceptual sampling of conscious object representations.

Common-onset masking (COM) refers to a methodology where a mask can impair awareness of an object if the mask's offset is delayed relative to the offset of the object. This method has classically been used to understand how discontinuities in visual input lead to the discrete removal of object representations before they reach conscious awareness. However, COM has recently been shown to reduce the precision of conscious object representations (Harrison, Rajsic, & Wilson, Psychonomic Bulletin & Review, 23(1), 180-186, 2016). As a result, Harrison et al. proposed that COM shortens the temporal window for perceptual sampling of an object's representation, an account consistent with interruption-based theories of masking. In the present study we modified the standard COM methodology to assess the impact of a delayed mask offset on the temporal perception of an object's representation. Across two experiments we provide novel evidence that a delayed mask offset can impair temporal perception of a conscious percept, such that it reduces the percept's perceived duration (Experiment 1), and prematurely terminates updating of the percept's dynamic orientation (Experiment 2). We refer to these results as temporal trimming, and suggest that the mechanism responsible for COM operates during the sustained perception of an object.

Object-substitution masking degrades the quality of conscious object representations.

Object-substitution masking (OSM) is a unique paradigm for the examination of object updating processes. However, existing models of OSM are underspecified with respect to the impact of object updating on the quality of target representations. Using two paradigms of OSM combined with a mixture model analysis we examine the impact of post-perceptual processes on a target's representational quality within conscious awareness. We conclude that object updating processes responsible for OSM cause degradation in the precision of object representations. These findings contribute to a growing body of research advocating for the application of mixture model analysis to the study of how cognitive processes impact the quality (i.e., precision) of object representations.