Hallucinations in schizophrenia, sensory impairment, and brain disease: a unifying model

Based on recent insight into the thalamocortical system and its role in perception and conscious experience, a unified pathophysiological framework for hallucinations in neurological and psychiatric conditions is proposed, which integrates previously unrelated neurobiological and psychological findings. Gamma-frequency rhythms of discharge activity from thalamic and cortical neurons are facilitated by cholinergic arousal and resonate in networks of thalamocortical circuits, thereby transiently forming assemblies of coherent gamma oscillations under constraints of afferent sensory input and prefrontal attentional mechanisms. If perception is based on synchronisation of intrinsic gamma activity in the thalamocortical system, then sensory input to specific thalamic nuclei may merely play a constraining role. Hallucinations can be regarded as underconstrained perceptions that arise when the impact of sensory input on activation of thalamocortical circuits and synchronisation of thalamocortical gamma activity is reduced. In conditions that are accompanied by hallucinations, factors such as cortical hyperexcitability, cortical attentional mechanisms, hyperarousal, increased noise in specific thalamic nuclei, and random sensory input to specific thalamic nuclei may, to a varying degree, contribute to underconstrained activation of thalamocortical circuits. The reticular thalamic nucleus plays an important role in suppressing random activity of relay cells in specific thalamic nuclei, and its dysfunction may be implicated in the biological vulnerability to hallucinations in schizophrenia. Combined with general activation during cholinergic arousal, this leads to excessive disinhibition in specific thalamic nuclei, which may allow cortical attentional mechanisms to recruit thalamic relay cells into resonant assemblies of gamma oscillations, regardless of their actual sensory input, thereby producing an underconstrained perceptual experience.     

Tightness shifts in the U.S. and China: Implications of tightening or loosening norms during the coronavirus pandemic

Emergent research identifies cultural tightness-looseness as an important factor for understanding cross-national outcome differences during the coronavirus pandemic. Because perceived tightness-looseness can be measured as an individual-level difference rather than a nation-level difference, and because tightness-looseness may shift during large-scale crises, we investigated whether such shifts occurred early in the coronavirus pandemic in both China (a relatively tight nation, n = 3642) and the U.S. (a relatively loose nation, n = 3583) across three cohorts. Tightness increased across cohorts in China and reduced across cohorts in the U.S. These changes transmitted corresponding indirect effects whereby compliance and institutional trust (scientific and government) about the pandemic were increased in China across cohorts, but decreased in the U.S. across cohorts. These patterns extend advice that national governments can increase compliance and trust via “tightening” by cautioning against norm-setters signaling the reverse (that norms about compliance are loose) given the outcomes observed in the U.S. samples.     

Effects of training with added difficulties on RADAR detection

Three experiments simulating military RADAR detection addressed a training difficulty hypothesis (training with difficulty promotes superior later testing performance) and a procedural reinstatement hypothesis (test performance improves when training conditions match test conditions). Training and testing were separated by 1 week. Participants detected targets (either alphanumeric characters or vehicle pictures) occurring among distractors. Two secondary tasks were used to increase difficulty (a concurrent, irrelevant tone‐counting task and a sequential, relevant action‐firing response). In Experiment 1 , involving alphanumeric targets with rapid displays, tone counting during training degraded test performance. In Experiment 2, involving vehicle targets with both sources of difficulty and slower presentation times, training under relevant difficulty aided test accuracy. In Experiment 3, involving vehicle targets and action firing with slow presentation times, test accuracy tended to be worst when neither training nor testing involved difficult conditions. These results show boundary conditions for the training difficulty and procedural reinstatement hypotheses. Copyright © 2010 John Wiley & Sons, Ltd.     

Summary knowledge of results for skill acquisition: support for the guidance hypothesis

Summary knowledge of results (KR) involves the presentation KR for each of a set of trials (e.g., 10) only after the last trial in the set has been completed. Earlier, Lavery (1962) showed that, relative to providing KR after each trial, a 20-trial summary KR was detrimental to performance in a practice phase with KR present but was beneficial for a no-KR retention test. Using a relatively simple ballistic-timing task, we examined summary lengths of 1 (essentially KR after every trial), 5, 10, and 15 trials, searching for an inverted-U relationship between summary length and retention performance as predicated by a guidance hypothesis for KR. During acquisition when KR was present and being manipulated, all groups showed improvements in performance across practice, while increased summary lengths generally depressed performance. However, in a delayed no-KR retention test, there was an inverse relation between the summary length in acquisition and absolute constant error on the retention test. A guidance hypothesis is favored to explain how, relative to immediate KR, long KR summaries can provide detrimental effects in acquisition while enhancing retention performance.     

Unawareness of impaired face recognition

We report investigations of the face processing abilities of SP, a right-handed woman who had suffered a subarachnoid haemorrhage from a right middle cerebral artery aneurysm. Although she could correctly assign visual stimuli to the 'face' category without difficulty, SP performed poorly on all other face processing, tasks, including 'closure' (Mooney faces), perception of facial expression, unfamiliar face matching, and identification of familiar faces. Identification of familiar people from nonfacial cues (names) remained relatively well-preserved, but severe impairments were evident on all face recognition tasks. Her errors mostly involved either failures to find a face familiar at all, or misidentification as another familiar person. In face-name learning tasks, there was evidence of 'covert' recognition of faces she failed to recognize overtly. SP's face processing impairment remained stable across a 20-month period of investigation, yet throughout this period she did not think that she had any problems in face recognition, and continued to show lack of insight into this impairment even when directly confronted with its consequences on formal testing. In contrast, SP showed adequate insight into other physical and cognitive impairments produced by her illness, including poor memory, hemiplegia, and hemianopia. We propose that her lack of insight into her face recognition problems involves a deficit-specific anosognosia, resulting from impairment of domain-specific monitoring abilities.     

Visual processing of stimulus compounds in newborn infants

An experiment is described in which newborn infants' processing of stimulus compounds was investigated. After familiarization to two alternately presented stimuli which differed in colour and orientation, the newborns showed significant preferences for a stimulus which had a novel colour/orientation combination: the novel stimulus was produced by recombining features of the stimuli used for familiarization. This finding argues against the view that infants initially process separate components, or parts, of visual stimuli and are only able to attend to the correlations between them after about 3 months of age. Rather, the ability to process and remember stimulus compounds is present at birth.     

Repetition Priming Follows Spontaneous but not Prompted Recognition of Familiar Faces

Reaction times to make a familiarity decision to the faces of famous people were measured after recognition of the faces in a pre-training phase had occurred spontaneously or following prompting with a name or other cue. At test, reaction times to familiar faces that had been recognized spontaneously in the pre-training phase were significantly facilitated relative to an unprimed comparison condition. Reaction times to familiar faces recognized only after prompting in the pre-training phase were not significantly facilitated. This was demonstrated both when a name prompt was used (Experiments 1 and 3) and when subjects were cued with brief semantic information (Experiment 2).

Repetition priming was not found to depend on prior spontaneous recognition per se. In Experiment 3, spontaneously recognizing a familiar face did not prime subsequent familiarity judgements when the same face had only been identified following prompting on a prior encounter. In Experiment 4, recognition memory for faces recognized after cueing was found to be over 90% accurate. This indicates that prompted recognition does not yield repetition priming, even though subjects can remember the faces. A fusion of “face recognition unit” and “episodic record” accounts of the repetition priming effect may be more useful than either theory alone in explaining these results.     

Priming of face matching in amnesia.

Priming was studied in a task that required a speeded response to photographs of faces. On each trial, subjects viewed two faces and decided if the same person was shown twice or if two different people were shown. Both familiar and unfamiliar (i.e., well-known and unknown) faces were used, and some face pairs were repeated with a mean delay of about 10 min. Repetition was associated with faster reaction times in young subjects (Experiment 1) as well as in amnesic patients and age-matched control subjects (Experiment 2). The patients' reaction times were slower overall, although the magnitude of the priming effect did not differ from that in the control subjects. This preservation of a normal reaction-time facilitation in subjects with impaired recognition memory for faces occurred for both familiar and unfamiliar faces, suggesting that amnesia does not necessarily interfere with the acquisition of new information as indexed by this priming effect.     

Imitation from 12 to 24 months in autism and typical development: a longitudinal Rasch analysis

The development of imitation during the second year of life plays an important role in domains of sociocognitive development such as language and social learning. Deficits in imitation ability in persons with autism spectrum disorder (ASD) from toddlerhood into adulthood have also been repeatedly documented, raising the possibility that early disruptions in imitation contribute to the onset of ASD and the deficits in language and social interaction that define the disorder. This study prospectively examined the development of imitation between 12 and 24 months of age in 154 infants at familial risk for ASD and 78 typically developing infants who were all later assessed at 36 months for ASD or other developmental delays. The study established a developmental measure of imitation ability and examined group differences over time, using an analytic Rasch measurement model. Results revealed a unidimensional latent construct of imitation and verified a reliable sequence of imitation skills that was invariant over time for all outcome groups. Results also showed that all groups displayed similar significant linear increases in imitation ability between 12 and 24 months and that these increases were related to individual growth in both expressive language and ratings of social engagement but not in fine motor development. The group of children who developed ASD by age 3 years exhibited delayed imitation development compared with the low-risk typical outcome group across all time-points, but were indistinguishable from other high-risk infants who showed other cognitive delays not related to ASD.