Brain mechanisms of extinction of the classically conditioned eyeblink response

It is well established that the cerebellum and its associated circuitry are essential for classical conditioning of the eyeblink response and other discrete motor responses (e.g., limb flexion, head turn, etc.) learned with an aversive unconditioned stimulus (US). However, brain mechanisms underlying extinction of these responses are still relatively unclear. Behavioral studies have demonstrated extinction as an active learning process distinct from acquisition. Experimental data in eyeblink conditioning suggest that plastic changes specific to extinction may play an important role in this process. Both cerebellar and hippocampal systems may be involved in extinction of these memories. The nature of this phenomenon and identification of the neural substrates necessary for extinction of originally learned responses is the topic of this review.     

Roll-over characteristics of human walking on inclined surfaces

Roll-over characteristics of able-bodied human subjects walking on ramped surfaces were examined in this study. Ten subjects walked at their normal self-selected speed on a level surface, a 5-deg ramp, and a 10-deg ramped surface. Ramps were designed such that ground reaction forces and center of pressure of the ground reaction forces could be measured on their surfaces. This set-up facilitated calculation of the effective rockers that the ankle-foot (AF) and knee-ankle-foot (KAF) systems conformed to during single-limb stance (contralateral toe off to contralateral heel contact). Since our original "roll-over shapes" were characterized between heel contact and opposite heel contact, we label the shapes found during single-limb stance as "truncated roll-over shapes". We hypothesized that the ankle-foot system would adapt to the various surfaces, creating a roll-over shape that would change in orientation with different levels of inclination. The truncated AF roll-over shapes supported this hypothesis for uphill walking but did not support the hypothesis for downhill walking. However, truncated roll-over shapes of the KAF system did adjust their orientation to match both the positive and negative levels of surface inclination. In general, the ankle appears to be the main adapting joint when walking up inclined surfaces while the knee becomes important for the overall adaptation in downhill walking. Knowledge of physiological lower-limb roll-over characteristics on ramped surfaces may help in the development of biomimetic prostheses and orthoses that will automatically adapt to changes in walking surface inclination.     

How does clients' method of payment influence psychologists' diagnostic decisions?

To what extent does payment method (managed care vs. out of pocket) influence the likelihood that an independent practitioner will assign a Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994) diagnosis to a client? When a practitioner does diagnose, how does payment method influence the specific choice of a diagnostic category? Independent practitioners responded to a vignette describing a fictitious client with symptoms of depression or anxiety. In half of the vignettes, the fictitious client intended to pay via managed care; in the other half, the fictitious client intended to pay out of pocket. Payment method had a very significant impact on diagnosis such that relative to out-of-pocket clients, managed care clients were much more likely to receive diagnoses and more likely to receive adjustment disorder diagnoses in particular. We discuss implications involving informed consent and other ethical issues.     

Constructing visual representations of natural scenes: the roles of short- and long-term visual memory

A "follow-the-dot" method was used to investigate the visual memory systems supporting accumulation of object information in natural scenes. Participants fixated a series of objects in each scene, following a dot cue from object to object. Memory for the visual form of a target object was then tested. Object memory was consistently superior for the two most recently fixated objects, a recency advantage indicating a visual short-term memory component to scene representation. In addition, objects examined earlier were remembered at rates well above chance, with no evidence of further forgetting when 10 objects intervened between target examination and test and only modest forgetting with 402 intervening objects. This robust prerecency performance indicates a visual long-term memory component to scene representation.     

Evaluating a split processing model of visual word recognition: effects of orthographic neighborhood size

The split fovea theory proposes that visual word recognition of centrally presented words is mediated by the splitting of the foveal image, with letters to the left of fixation being projected to the right hemisphere (RH) and letters to the right of fixation being projected to the left hemisphere (LH). Two lexical decision experiments aimed to elucidate word recognition processes under the split fovea theory are described. The first experiment showed that when words were presented centrally, such that the initial letters were in the left visual field (LVF/RH), there were effects of orthographic neighborhood, i.e., there were faster responses to words with high rather than low orthographic neighborhoods for the initial letters ('lead neighbors'). This effect was limited to lead-neighbors but not end-neighbors (orthographic neighbors sharing the same final letters). When the same words were fully presented in the LVF/RH or right visual field (RVF/LH, Experiment 2), there was no effect of orthographic neighborhood size. We argue that the lack of an effect in Experiment 2 was due to exposure to all of the letters of the words, the words being matched for overall orthographic neighborhood count and the sub-parts no longer having a unique effect. We concluded that the orthographic activation found in Experiment 1 occurred because the initial letters of centrally presented words were projected to the RH. The results support the split fovea theory, where the RH has primacy in representing lead neighbors of a written word.     

The precise time course of lexical activation: MEG measurements of the effects of frequency, probability, and density in lexical decision

Visually presented letter strings consistently yield three MEG response components: the M170, associated with letter-string processing (Tarkiainen, Helenius, Hansen, Cornelissen, & Salmelin, 1999); the M250, affected by phonotactic probability, (Pylkk?nen, Stringfellow, & Marantz, 2002); and the M350, responsive to lexical frequency (Embick, Hackl, Schaeffer, Kelepir, & Marantz, 2001). Pylkk?nen et al. found evidence that the M350 reflects lexical activation prior to competition among phonologically similar words. We investigate the effects of lexical and sublexical frequency and neighborhood density on the M250 and M350 through orthogonal manipulation of phonotactic probability, density, and frequency. The results confirm that probability but not density affects the latency of the M250 and M350; however, an interaction between probability and density on M350 latencies suggests an earlier influence of neighborhoods than previously reported.     

Differential effects of manual assisted cognitive behavior therapy in the treatment of recurrent deliberate self-harm and personality disturbance: the POPMACT study

A total of 480 patients were treated in a large, multicenter randomized trial of a brief form of cognitive therapy, manual-assisted cognitive behavior therapy (MACT) versus treatment as usual (TAU) for recurrent deliberate self-harm. Each patient was randomized after a self-harm episode assessed at an accident and emergency center and followed up over 1 year. The main hypothesis tested was that those allocated to MACT would have a lower proportion of self-harm episodes in the succeeding year. A total of 60% of those allocated to MACT had face-to-face treatment and 430 (90%) of all patients had self-harm data recorded after 1 year. Although the results showed no significant difference between those repeating self-harm in the MACT group (39%) compared with the TAU group (46%) (P = 0.20), the treatment was cost effective (10% cheaper than TAU) and the frequency of self-harm episodes was fewer (50%) in the MACT group. A total of nine of 10 patients had some personality disturbance (42% of these with disorder), and for those where information on parasuicide events was collected, the proportion having a repeat episode ranged from 33% to 63% for different personality disorders. Those with BPD were most likely to repeat episodes quickly (mean 89 days for 25% to repeat) with dissocial personality disorder (equivalent mean 384 days) the slowest to repeat. Total costs were significantly greater in those with personality disorder and were reduced in those allocated to MACT; this saving was reversed in those with borderline disorder. On average, MACT appeared to increase the cost of those patients with BPD (BPD) and reduce the cost of those with other personality disorders. It is concluded that MACT has value in preventing self-harm cost effectively but this appears to be confined mainly to those who do not have BPD.     

Childhood maltreatment associated with adult personality disorders: findings from the Collaborative Longitudinal Personality Disorders Study

Adverse childhood experiences such as abuse and neglect are frequently implicated in the development of personality disorders (PDs); however, research on the childhood histories of most PD groups remains limited. In this multisite investigation, we assessed self-reported history of abuse and neglect experiences among 600 patients diagnosed with either a PD (borderline, schizotypal, avoidant, or obsessive-compulsive) or major depressive disorder without PD. Results indicate that rates of childhood maltreatment among individuals with PDs are generally high (73% reporting abuse; 82% reporting neglect). As expected, borderline PD was more consistently associated with childhood abuse and neglect than other PD diagnoses. However, even when controlling for the effect of borderline PD, other PD diagnoses were associated with specific types of maltreatment.     

Gaze-contingent displays: a review.

Gaze-contingent displays (GCDs) attempt to balance the amount of information displayed against the visual information processing capacity of the observer through real-time eye movement sensing. Based on the assumed knowledge of the instantaneous location of the observer's focus of attention, GCD content can be "tuned" through several display processing means. Screen-based displays alter pixel level information generally matching the resolvability of the human retina in an effort to maximize bandwidth. Model-based displays alter geometric-level primitives along similar goals. Attentive user interfaces (AUIs) manage object- level entities (e.g., windows, applications) depending on the assumed attentive state of the observer. Such real-time display manipulation is generally achieved through non-contact, unobtrusive tracking of the observer's eye movements. This paper briefly reviews past and present display techniques as well as emerging graphics and eye tracking technology for GCD development.