Punit Shah

A Critical Review of Non-carious Cervical (Wear) Lesions and the Role of Abfraction, Erosion, and Abrasion

The terms ‘abfraction’ and ‘abrasion’ describe the cause of lesions found along the cervical margins of teeth. Erosion, abrasion, and attrition have all been associated with their formation. Early research suggested that the cause of the V-shaped lesion was excessive horizontal toothbrushing. Abfraction is another possible etiology and involves occlusal stress, producing cervical cracks that predispose the surface to erosion and abrasion. This article critically reviews the literature on abrasion, erosion, and abrasion, and abfraction. The references were obtained by a MEDLINE search in March, 2005, and from this, hand searches were undertaken. From the literature, there is little evidence, apart from laboratory studies, to indicate that abfraction exists other than as a hypothetical component of cervical wear.

Toward a Neurobiology of Unrealistic Optimism

Research spanning three decades has found that human judgment is characterized by unrealistic optimism (or “optimism bias”), the tendency to underestimate the likelihood of negative events and overestimate the likelihood of positive events (Weinstein, 1980). This work has recently garnered much interest, some question its existence (Harris and Hahn, 2011), while others have found support for it by using novel experiments (Massey et al., 2011; Simmons and Massey, 2012). Most recently, attention has turned to investigating the neural underpinnings of this phenomenon (Sharot et al., 2007, 2011). A new study (Sharot et al., 2012) has now shown that optimism bias is increased by up-regulating dopaminergic function via dihydroxy-l-phenylalanine (l-DOPA). Sharot et al. (2012) propose that this process occurs as l-DOPA attenuates belief updating in response to bad news about the future. In light of such evidence, the implications for future research on unrealistic optimism are discussed. Unrealistic optimism is recognized as one of the major human cognitive biases (Kahneman, 2011). It has been the focus of much research, particularly in social and clinical psychology; here it is argued that optimism bias is not just a pervasive feature of human judgment, but a crucial requirement to guard against depression (Taylor and Brown, 1988). Despite the wealth of research, this work has been scrutinized, as many question (e.g., Moore and Small, 2008) the methods used in the majority of studies where the “comparison approach” is used, i.e., where optimism bias is interpreted by optimistic comparisons of one’s personal risk, relative to the average person. A compelling demonstration of how optimism research may be riddled with statistical artifacts has recently emerged (Harris and Hahn, 2011). In contrast, Sharot et al. (2011) provided a promising, new approach to investigate optimism bias, via the concept of belief change. Sharot and colleagues reported that unrealistic optimism persists “in the face of reality” because good (versus bad) news is incorporated significantly more into one’s beliefs of personal risk. They reported that this asymmetric “updating” originates from a prediction error bias which correlates (determined by functional magnetic resonance imaging) with activity in various regions of the frontal cortex. Importantly, on first glance, this method does not appear to suffer from the problems inherent in the comparison approach of optimism research, and their findings have been interpreted as evidence of unrealistic optimism. This has naturally shifted attention towards the neurobiology underlying this phenomenon. In their new study published in Current Biology, Sharot et al. (2012) go further, by demonstrating how the differential updating reported previously (Sharot et al., 2011), is modulated by administering l-DOPA as belief updating for bad news becomes impaired. Sharot et al. used the same belief update task employed in 2011; they asked participants to estimate their likelihood of experiencing negative life events. Subjects were then asked to provide a second estimate for each of the events, but only after being given the actual probability for that event to occur to someone of the same socio-economic background. Optimism bias was measured by the degree to which participants updated their personal risk from their first and second estimate; the mean update in response to good news was then compared to the mean update for bad news. The crucial manipulation, however, was administration of l-DOPA during the task. l-DOPA is a pre-cursor for the monoamine neuromodulator dopamine, and when administered orally, it increases dopaminergic activity within the brain. Dopamine was chosen as it is known to modulate reward learning (e.g., Berridge and Robinson, 1998) and therefore, it was expected to either enhance belief updating concerning good news and/or diminish updating in response to the bad news. In order to investigate this, subjects completed the belief update task on two separate days. On each day a different set of 40 negative life events were presented. Employing a double-blind procedure, they were given l-DOPA on one occasion and received a placebo on the second occasion. This order was fully counterbalanced. In addition, a control group of participants were administered Citalopram (a Selective Serotonin Reuptake Inhibitor frequently prescribed for the treatment of depression; Trivedi et al., 2006) instead of l-DOPA. Serotonin was identified as an alternative monoaminergic neuromodulator, given the association between optimism bias and depression (Strunk et al., 2006). As predicted, up-regulating dopamine function increased optimistic bias; that is, when the degree of belief update was compared across the two conditions (drug versus placebo), it was significantly reduced for bad news (or “undesirable information”) when l-DOPA had been administered. There was no such pattern in the control group who received Citalopram. When update scores were analyzed, a significant Condition (l-DOPA/placebo) × Desirability (desirable/undesirable information) interaction, when coupled with post hoc tests, revealed that belief update was not modulated by enhanced learning of desirable information. Rather, when l-DOPA was administered, there was significantly diminished belief updating in response to undesirable information, compared to the placebo condition. Hence, Sharot and colleagues inferred that unrealistic optimism is evident, as negative events are consistently underestimated as a result of selective belief updating. Sharot and colleagues have furthered our understanding of unrealistic optimism: the shift of optimism research into the realm of cognitive neuroscience is encouraging and the conclusions resulting from this latest study are clear: optimism bias is a robust phenomenon with a neurobiological basis. This supports Simmons and Massey’s (2012) recent suggestion, calling for a shift from “whether optimism is a real phenomenon to when and why it emerges” (p. 5). Indeed, Sharot et al. (2011, 2012) go some way to elucidate the possible mechanisms underlying this phenomenon; however, it seems prudent to examine this new approach of investigating unrealistic optimism with the same rigor as the old comparison approach in future research. Particularly, as the sole use of negative events in optimism studies has been shown to be problematic (see Harris and Hahn, 2011). It is clear, however, the continued use of neuroscientific techniques in this field is an exciting prospect – particularly if we are to better understand optimism bias and its impact on mental health.

Alexithymia, Not Autism, Predicts Poor Recognition of Emotional Facial Expressions

Despite considerable research into whether face perception is impaired in autistic individuals, clear answers have proved elusive. In the present study, we sought to determine whether co-occurring alexithymia (characterized by difficulties interpreting emotional states) may be responsible for face-perception deficits previously attributed to autism. Two experiments were conducted using psychophysical procedures to determine the relative contributions of alexithymia and autism to identity and expression recognition. Experiment 1 showed that alexithymia correlates strongly with the precision of expression attributions, whereas autism severity was unrelated to expression-recognition ability. Experiment 2 confirmed that alexithymia is not associated with impaired ability to detect expression variation; instead, results suggested that alexithymia is associated with difficulties interpreting intact sensory descriptions. Neither alexithymia nor autism was associated with biased or imprecise identity attributions. These findings accord with the hypothesis that the emotional symptoms of autism are in fact due to co-occurring alexithymia and that existing diagnostic criteria may need to be revised.

Alexithymia, not autism, is associated with impaired interoception

It has been proposed that Autism Spectrum Disorder (ASD) is associated with difficulties perceiving the internal state of ones body (i.e., impaired interoception), causing the socio-emotional deficits which are a diagnostic feature of the condition. However, research indicates that alexithymia – characterized by difficulties in recognizing emotions from internal bodily sensations – is also linked to atypical interoception. Elevated rates of alexithymia in the autistic population have been shown to underpin several socio-emotional impairments thought to be symptomatic of ASD, raising the possibility that interoceptive difficulties in ASD are also due to co-occurring alexithymia. Following this line of inquiry, the present study examined the relative impact of alexithymia and autism on interoceptive accuracy (IA). Across two experiments, it was found that alexithymia, not autism, was associated with atypical interoception. Results indicate that interoceptive impairments should not be considered a feature of ASD, but instead due to co-occurring alexithymia.

The 20-item prosopagnosia index (PI20): a self-report instrument for identifying developmental prosopagnosia.

Self-report plays a key role in the identification of developmental prosopagnosia (DP), providing complementary evidence to computer-based tests of face recognition ability, aiding interpretation of scores. However, the lack of standardized self-report instruments has contributed to heterogeneous reporting standards for self-report evidence in DP research. The lack of standardization prevents comparison across samples and limits investigation of the relationship between objective tests of face processing and self-report measures. To address these issues, this paper introduces the PI20; a 20-item self-report measure for quantifying prosopagnosic traits. The new instrument successfully distinguishes suspected prosopagnosics from typically developed adults. Strong correlations were also observed between PI20 scores and performance on objective tests of familiar and unfamiliar face recognition ability, confirming that people have the necessary insight into their own face recognition ability required by a self-report instrument. Importantly, PI20 scores did not correlate with recognition of non-face objects, indicating that the instrument measures face recognition, and not a general perceptual impairment. These results suggest that the PI20 can play a valuable role in identifying DP. A freely available self-report instrument will permit more effective description of self-report diagnostic evidence, thereby facilitating greater comparison of prosopagnosic samples, and more reliable classification.

Robust orienting to protofacial stimuli in autism.

Summary Newborn infants exhibit a remarkable tendency to orient to faces. This behavior is thought to be mediated by a subcortical mechanism tuned to the protoface stimulus: a face-like configuration comprising three dark areas on a lighter background. When this unique stimulus translates across their visual field, neurotypical infants will change their gaze or head direction to track the protoface [1–3]. Orienting to this low spatial frequency pattern is thought to encourage infants to attend to faces, despite their poor visual acuity [2,3]. By biasing the input into the newborn’s visual system, this primitive instinct may serve to ‘canalize’ the development of more sophisticated face representation. Leading accounts attribute deficits of face perception associated with Autism Spectrum Disorders (ASD) [4] to abnormalities within this orienting mechanism. If infants who are later diagnosed with ASD exhibit reduced protoface orienting, this may compromise the emergence of perceptual expertise for faces [5]. Here we report a novel effect that confirms that the protoface stimulus captures adults’ attention via an involuntary, exogenous process (Experiment 1). Contrary to leading developmental accounts of face perception deficits in ASD, we go on to show that this orienting response is intact in autistic individuals (Experiment 2).

Self-other control: a candidate mechanism for social cognitive function

Despite ever-growing interest in the “social brain” and the search for the neural underpinnings of social cognition, we are yet to fully understand the basic neurocognitive mechanisms underlying complex social behaviors. One such candidate mechanism is the control of neural representations of the self and of other people (Brass et al., 2009; Spengler et al., 2009a), and it is likely that “common” disorders of social cognition such as autism and schizophrenia involve atypical modulation of self and other representations (Cook and Bird, 2012; Ferri et al., 2012). This opinion piece will first consider self-other control as a possible low-level neurocognitive mechanism for social functioning across many domains of social cognition. Neuroscientific evidence will be drawn upon and the potential for a better understanding and identification of neuropsychological markers for atypical social cognitive development, discussed.

Intact facial adaptation in autistic adults

Adaptation paradigms seek to bias subsequently viewed stimuli through prolonged exposure to an adapting stimulus, thereby giving rise to an aftereffect. Recent experiments have found that children with autism spectrum disorders (ASD) show reduced facial aftereffects, prompting some researchers to speculate that all individuals with ASD exhibit deficient facial adaptation. However, caution is required when generalizing findings from samples of children with ASD to the wider ASD population. The reduced facial aftereffects seen in child samples may instead reflect delayed or atypical developmental trajectories, whereby individuals with ASD are slower to develop adaptive mechanisms. In the present study, two experiments were conducted to determine whether high‐functioning adults with ASD also show diminished aftereffects for facial identity and expression. In Experiment 1, using a procedure that minimized the contribution of low‐level retinotopic adaptation, we observed substantial aftereffects comparable to those seen in matched controls, for both facial identity and expression. A similar pattern of results was seen in Experiment 2 using a revised procedure that increased the contribution of retinotopic adaptation to the facial aftereffects observed. That adults with autism can show robust facial aftereffects raises the possibility that group differences are seen only at particular points during development, and may not be a lifelong feature of the condition. Autism Res 2014, 7: 481–490.

Reputation management: evidence for ability but reduced propensity in autism.

Previous research has reported that autistic adults do not manage their reputation, purportedly due to problems with theory of mind [Izuma, Matsumoto, Camerer, & Adolphs]. The current study aimed to test alternative explanations for this apparent lack of reputation management. Twenty typical and 19 autistic adults donated to charity and to a person, both when alone and when observed. In an additional manipulation, for half of the participants, the observer was also the recipient of their donations, and participants were told that this observer would subsequently have the opportunity to donate to them (motivation condition). This manipulation was designed to encourage an expectation of a reciprocal “tit‐for‐tat” strategy in the participant, which may motivate participants to change their behavior to receive more donations. The remaining participants were told that the person watching was just observing the procedure (no motivation condition). Our results replicated Izuma et al.s finding that autistic adults did not donate more to charity when observed. Yet, in the motivation condition, both typical and autistic adults donated significantly more to the observer when watched, although this effect was significantly attenuated in autistic individuals. Results indicate that, while individuals with autism may have the ability to think about reputation, a reduced expectation of reciprocal behavior from others may reduce the degree to which they engage in reputation management. Autism Res 2013, ●●: ●●–●●.

Probing short-term face memory in developmental prosopagnosia

It has recently been proposed that the face recognition deficits seen in neurodevelopmental disorders may reflect impaired short-term face memory (STFM). For example, introducing a brief delay between the presentation of target and test faces seems to disproportionately impair matching or recognition performance in individuals with Autism Spectrum Disorders. The present study sought to determine whether deficits of STFM contribute to impaired face recognition seen in Developmental Prosopagnosia. To determine whether developmental prosopagnosics exhibit impaired STFM, the present study used a six-alternative-forced-choice match-to-sample procedure. Memory demand was manipulated by employing a short or long delay between the presentation of the target face, and the six test faces. Crucially, the perceptual demands were identical in both conditions, thereby allowing the independent contribution of STFM to be assessed. Prosopagnosics showed clear evidence of a category-specific impairment for face-matching in both conditions; they were both slower and less accurate than matched controls. Crucially, however, the prosopagnosics showed no evidence of disproportionate face recognition impairment in the long-interval condition. While individuals with DP may have problems with the perceptual encoding of faces, it appears that their representations are stable over short durations. These results suggest that the face recognition difficulties seen in DP and autism may be qualitatively different, attributable to deficits of perceptual encoding and perceptual maintenance, respectively.