Corticostriatal responses to social reward are linked to trait reward sensitivity and subclinical substance use in young adults

Aberrant levels of reward sensitivity have been linked to substance use disorder and are characterized by alterations in reward processing in the ventral striatum (VS). Less is known about how reward sensitivity and subclinical substance use relate to striatal function during social rewards (e.g., positive peer feedback). Testing this relation is critical for predicting risk for development of substance use disorder. In this pre-registered study, participants (N=44) underwent fMRI while completing well-matched tasks that assess neural response to reward in social and monetary domains. Contrary to our hypotheses, aberrant reward sensitivity blunted the relationship between substance use and striatal activation during receipt of rewards, regardless of domain. Moreover, exploratory whole-brain analyses showed unique relations between substance use and social rewards in temporoparietal junction. Psychophysiological interactions demonstrated that aberrant reward sensitivity is associated with increased connectivity between the VS and ventromedial prefrontal cortex during social rewards. Finally, we found that substance use was associated with decreased connectivity between the VS and dorsomedial prefrontal cortex for social rewards, independent of reward sensitivity. These findings demonstrate nuanced relations between reward sensitivity and substance use, even among those without substance use disorder, and suggest altered reward-related engagement of cortico-VS responses as potential predictors of developing disordered behavior.

Social Context and Reward Sensitivity Enhance Corticostriatal Function during Experiences of Shared Rewards

Although prior research has demonstrated enhanced striatal response when sharing rewards with close social connections, less is known about how individual differences affect ventral striatal (VS) activation and connectivity when experiencing rewards within social contexts. Given that self-reported reward sensitivity and level of substance use have been associated with differences in VS activation, we set out to investigate whether these factors would be independently associated with enhancements to neural reward responses within social contexts. In this pre-registered study, participants (N=45) underwent fMRI while playing a card guessing game in which correct or incorrect guesses resulted in monetary gains and losses that were shared evenly with either a close friend, stranger (confederate), or non-human partner. Consistent with our prior work, we found increased VS activation when sharing rewards with a socially close peer as opposed to an out-of-network stranger. As self-reported reward sensitivity increased, the difference in VS response to rewards shared with friends and strangers decreased. We also found enhanced connectivity between the VS and temporoparietal junction when sharing rewards with close friends as opposed to strangers. Finally, exploratory analyses revealed that as reward sensitivity and sub-clinical substance use increase, the difference in VS connectivity with the right fusiform face area increases as a function of social context. These findings demonstrate that responsivity to the context of close friends may be tied to individual reward sensitivity or sub-clinical substance use habits; together these factors may inform predictions of risk for future mental health disorders.

Properties of graphic motor plans in the writing system

The present study explores the extent to which properties of abstract graphemic representations are maintained at the post-graphemic level of graphic motor plans, where the sequences of writing strokes for producing the letters in a word are represented. On the basis of results from a stroke patient (NGN) who has a deficit affecting the activation of graphic motor plans, we explore the post-graphemic representation of 1) consonant/vowel status of letters; 2) geminate (double) letters, such as the BB in RABBIT; and 3) digraphs, such as the SH in SHIP. Through analyses of NGN's letter substitution errors, we conclude that 1) consonant-vowel status is not represented at the level of graphic motor plans; 2) geminates have special representations at the motor-plan level, as at the graphemic level; and 3) digraphs are represented by two separate single-letter graphic motor plans, and not by unitary digraph motor plans.

Do animals dream?

The understanding of biological functions of sleep has improved recently, including an understanding of the deep evolutionary roots of sleep among animals. However, dreaming as an element of sleep may be particularly difficult to address in non-human animals because in humans dreaming involves a non-wakeful form of awareness typically identified through verbal report. Here, we argue that parallels that exist between the phenomenology, physiology, and sleep behaviors during human dreaming provide an avenue to investigate dreaming in non-human animals. We review three alternative measurements of human dreaming - neural correlates of dreaming, 'replay' of newly-acquired memories, and dream-enacting behaviors - and consider how these may be applied to non-human animal models. We suggest that while animals close in brain structure to humans (such as mammals and birds) may be optimal models for the first two of these measurements, cephalopods, especially octopuses, may be particularly good candidates for the third.

Hyperoxaemia and hypoxaemia are associated with harm in patients with ARDS

BACKGROUND

Oxygen therapy is routinely administered to mechanically ventilated patients. However, there remains uncertainty about the optimal oxygen titration target in patients with the acute respiratory distress syndrome (ARDS).

METHODS

Prospectively identified adult patients meeting the Berlin definition of ARDS between 1st January 2014 and 13th December 2016 were analyzed. Oxygen exposure variables were collected at 6-hourly intervals. The primary exposure was the average time-weighted partial pressure of arterial oxygen (PaO2) calculated over a maximum of 7 days from meeting ARDS criteria. The primary outcome was ICU mortality. Univariable and multivariable logistic regression analyses were performed to assess the impact of exposure variables on clinical outcomes. Results are presented as odds ratio [95% confidence interval].

RESULTS

202 patients were included in the final analysis. Overall ICU mortality was 31%. The average time-weighted PaO2 during the first 7 days of ARDS was similar between non-survivors and survivors (11.3 kPa [10.2, 12.5] (84.8 mmHg [76.5, 93.8]) vs. 11.9 kPa [10.9, 12.6] (89.3 mmHg [81.8, 94.5]); p = 0.08). In univariable and multivariable analysis, average time-weighted PaO2 demonstrated a U-shaped relationship with ICU mortality. There was a similar relationship identified with hospital mortality.

CONCLUSIONS

In patients with ARDS, the predicted probability of both ICU and hospital mortality was lowest when the average time-weighted PaO2 was between 12.5 and 14 kPa (93.8-105.0 mmHg), suggesting this is a reasonable oxygenation target for clinicians to aim for.

Reading proficiency influences the effects of transcranial direct current stimulation: Evidence from selective modulation of dorsal and ventral pathways of reading in bilinguals

INTRODUCTION

tDCS can modulate reading which is processed by lexical (ventral) and sub-lexical (dorsal) pathways. Previous research indicates that pathway recruitment in bilinguals depends on a script's orthographic depth and a reader's proficiency with it. The effect of tDCS on each reading pathway has not been investigated in bilinguals. We stimulated the left dorsal and ventral pathways separately in Chinese-English (C-E) bilinguals to understand whether pathway-specific modulation by tDCS is possible and, if so, how it is influenced by orthographic depth and script proficiency.

METHODS

A double-blind, sham-controlled, within-subject experiment was designed wherein 16 balanced bilinguals received anodal tDCS in dorsal, ventral and sham sessions. Two tDCS montages of electrode sizes 5 × 5 cm² with 1) anode at CP5 and cathode at CZ, and 2) anode at TP7 and cathode at nape of the neck, were applied for stimulating the dorsal and ventral pathways respectively. Bilinguals were asked to read word lists for each language before and after stimulation. RTs for accurate trials were analysed using linear mixed-effect modelling that included proficiency scores for reading English pseudo-words (PW) and Chinese pinyin.

RESULTS

For both languages, word reading RTs were faster following dorsal pathway stimulation. The dorsal stimulation effect (change in RT) was negatively correlated with pseudoword reading and pinyin proficiency. Stimulation of the ventral pathway decreased RTs only for Chinese reading.

CONCLUSION

Dorsal and ventral reading pathways can be selectively modulated by tDCS in bilingual readers with dorsal (sub-lexical) pathway stimulation affecting reading in both scripts and ventral (lexical) pathway stimulation selectively affecting Chinese reading. Dorsal pathway tDCS effects are modulated by sub-lexical reading proficiency.

Functions of ventral visual cortex after bilateral medial temporal lobe damage

Repeated stimuli elicit attenuated responses in visual cortex relative to novel stimuli. This adaptation can be considered as a form of rapid learning and a signature of perceptual memory. Adaptation occurs not only when a stimulus is repeated immediately, but also when there is a lag in terms of time and other intervening stimuli before the repetition. But how does the visual system keep track of which stimuli are repeated, especially after long delays and many intervening stimuli? We hypothesized that the hippocampus and medial temporal lobe (MTL) support long-lag adaptation, given that this memory system can learn from single experiences, maintain information over delays, and send feedback to visual cortex. We tested this hypothesis with fMRI in an amnesic patient, LSJ, who has encephalitic damage to the MTL resulting in extensive bilateral lesions including complete hippocampal loss. We measured adaptation at varying time lags between repetitions in functionally localized visual areas that were intact in LSJ. We observed that these areas track information over a few minutes even when the hippocampus and extended parts of the MTL are unavailable. LSJ and controls were identical when attention was directed away from the repeating stimuli: adaptation occurred for lags up to three minutes, but not six minutes. However, when attention was directed toward stimuli, controls now showed an adaptation effect at six minutes but LSJ did not. These findings suggest that visual cortex can support one-shot perceptual memories lasting for several minutes but that the hippocampus and surrounding MTL structures are necessary for adaptation in visual cortex after longer delays when stimuli are task-relevant.

Bimanual visually guided movements are more than the sum of their parts: Evidence from optic ataxia

Many reaching actions involve both hands. An open question is whether two-handed reaching involves two simultaneous, independent unimanual reaches, or recruits additional or different processes than those mediating one-handed reaching. We tested optic ataxic patient MDK on a set of unimanual and bimanual reaching tasks. Although MDK was impaired in both types of reaching task, his bimanual reaching was considerably better than his unimanual reaching. These results imply that bimanual reaching involves different or additional processes relative to unimanual reaching. We suggest that bimanual reaching may involve monitoring of the distance between the two hands relative to the distance between the two targets.

How are object shape axes defined? Evidence from mirror-image confusions

A central goal in research on visual perception is to understand how the visual system represents the shapes of objects. According to many theorists, axes defined on the basis of object geometry provide a coordinate system for representing the locations and orientations of object parts. An important question that has received little attention concerns how object axes are defined-that is, what aspects of object geometry determine how axes are assigned to shapes? We evaluated 2 hypotheses. According to the elongated-part hypothesis, axes are defined on the basis an object's most elongated part, such that, for example, the principal axis for a hatchet would coincide with the long axis of the hatchet's handle. In contrast, the global-shape hypothesis holds that axes are defined on the basis of an object's overall shape (e.g., for the hatchet, as the longest axis that spans the entire hatchet). Using a novel paradigm involving analysis of mirror-image confusions, we obtained evidence strongly supporting the elongated-part hypothesis. Our results also point to a role for secondary as well as principal axes in object shape representation. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

A deficit in post-graphemic writing processes: Evidence for a graphomotor buffer

Post-graphemic writing processes transform abstract letter representations into representations of writing movements. We describe an individual with an acquired post-graphemic writing deficit. NGN is normal in spelling words aloud, but impaired in writing words to dictation, with most errors involving letter substitutions (e.g., RUMOR written as BUMOR). NGN's deficit affects graphic motor plans, which specify the writing strokes for producing letters. Analyses of writing speed, fluency, and stroke patterns suggest that NGN's errors result from incomplete motor-plan activation. NGN's error rate is high for the first letter in a word, and declines across subsequent positions. On the basis of this serial position effect and other results, we propose that post-graphemic writing mechanisms include a graphomotor buffer, a writing-specific working memory that holds activated graphic motor plans bound to specific serial positions. We suggest that NGN's graphomotor buffer is damaged such that early serial positions are affected most severely. Finally, we present results speaking to the roles and capabilities of the graphomotor buffer, and the structure of graphic motor plans.

The devil's in the g-tails: Deficient letter-shape knowledge and awareness despite massive visual experience

Knowledge of letter shapes is central to reading. In experiments focusing primarily on a single letter shape-the "looptail" lowercase print G-we found surprising gaps in skilled readers' knowledge. In Experiment 1 most participants failed to recall the existence of looptail g when asked if G has two lowercase print forms, and almost none were able to write looptail g accurately. In Experiment 2 participants searched for Gs in text with multiple looptail gs. Asked immediately thereafter to write the g form they had seen, half the participants produced an "opentail" g (the typical handwritten form), and only one wrote looptail g accurately. In Experiment 3 participants performed poorly in discriminating looptail g from distractors with important features mislocated or misoriented. These results have implications for understanding types of knowledge about letters, and how this knowledge is acquired. For example, our findings speak to hypotheses concerning the role of writing in learning letter shapes. More generally, our findings raise questions about the conditions under which massive exposure does, and does not, yield detailed, accurate, accessible knowledge. In this context we relate our findings to studies showing poor knowledge or memory for various types of stimuli despite extensive exposure. (PsycINFO Database Record

Motivational Interviewing for Victims of Armed Community Violence: A Nonexperimental Pilot Feasibility Study

OBJECTIVE

The present study aimed to develop a novel, hospital-based motivational interviewing (MI) intervention for victims of armed community violence (MI-VoV) targeting patient-specific risk factors for future violence or violent victimization.

METHOD

This uncontrolled pilot feasibility study examined a sample of patients (n = 71) hospitalized due to violent injury at a Level 1 Trauma Center in [Location Redacted for Masked Review] between January 2013 and May 2014. Patients first participated in a brief assessment to identify risk factors for violence/violent injury. A single MI session then targeted risk behaviors identified for each patient. Proximal outcomes, including motivation for change and behaviors to reduce risk, were examined at 2 weeks and 6-12 weeks post-discharge. Distal outcomes, including fighting, weapon-carrying, and gun-carrying, and other violence risk factors were examined at 6-12 week follow-up.

RESULTS

Ninety-five patients were offered participation, 79 (83.2%) agreed to participate, and 73 (76.8%) completed the risk assessment. Of these, 71 had at least one violence/violent injury risk factor. Behaviors to reduce risk were significantly greater at two-week and 6-12 week follow-up (ps < .05). Fighting, weapon-carrying, gun-carrying were significantly reduced at 6-12 week follow-up (p < .05).

CONCLUSIONS

This intervention appears to be feasible to implement and acceptable to patients. A randomized controlled trial evaluating efficacy appears warranted.

Cognitive processes in spatial mapping: Evidence from a developmental spatial deficit

We report a case study of an adolescent girl (N.K.Y.) with a developmental deficit affecting spatial processing. In a simple spatial mapping task, N.K.Y. shows a striking dissociation: She succeeds in one variant of the experiment in which the stimuli are objects, but struggles in a structurally identical task with people as stimuli. We present evidence that this dissociation stems from a tendency to automatically adopt the spatial perspective of other people, but not objects-a phenomenon also observed in neurotypical individuals. When adopting another person's perspective, N.K.Y. imagines herself in the other's position, representing the other's left and right as if it were her own. N.K.Y.'s deficit in relating left-right information to her own body then disrupts her performance. Our results shed light on the nature of N.K.Y.'s deficit as well as the cognitive operations involved in spatial perspective taking.

Do reading and spelling share orthographic representations? Evidence from developmental dysgraphia

Both spelling and reading depend on knowledge of the spellings of words. Despite this commonality, observed dissociations between spelling and reading in cases of acquired and developmental deficits suggest some degree of independence between the cognitive mechanisms involved in these skills. In this paper, we examine the relationship between spelling and reading in two children with developmental dysgraphia. For both children, we identified significant deficits in spelling that affected the processing of orthographic long-term memory representations of words. We then examined their reading skills for similar difficulties. Even with extensive testing, we found no evidence of a reading deficit for one of the children. We propose that there may be an underlying difficulty that specifically affects the learning of orthographic word representations for spelling. These results lead us to conclude that at least some components of lexical orthographic representation and processing develop with considerable independence in spelling and reading.

The value of cognitive neuropsychology: The case of vision research

Cognitive neuropsychological evidence is widely viewed as inherently flawed or weak, despite well-reasoned arguments to the contrary by many theorists. Rather than attempting yet another defence of cognitive neuropsychology on logical grounds, we point out through examples that in practice, cognitive neuropsychological evidence is widely accepted as valid and important, and has had a major impact on cognitive theory and research. Objections offered in the abstract rarely arise in the context of actual studies. We develop these points through examples from the domain of vision, discussing cerebral achromatopsia and akinetopsia, selective impairment and sparing of face recognition, perception-action dissociations, and blindsight.

Developmental dysgraphia: An overview and framework for research

Developmental deficits in the acquisition of writing skills (developmental dysgraphias) are common and have significant consequences, yet these deficits have received relatively little attention from researchers. We offer a framework for studying developmental dysgraphias (including both spelling and handwriting deficits), arguing that research should be grounded in theories describing normal cognitive writing mechanisms and the acquisition of these mechanisms. We survey the current state of knowledge concerning developmental dysgraphia, discussing potential proximal and distal causes. One conclusion emerging from this discussion is that developmental writing deficits are diverse in their manifestations and causes. We suggest an agenda for research on developmental dysgraphia, and suggest that pursuing this agenda may contribute not only to a better understanding of developmental writing impairment, but also to a better understanding of normal writing mechanisms and their acquisition. Finally, we provide a brief introduction to the subsequent articles in this special issue on developmental dysgraphia.

Networks and Theories: The Place of Connectionism in Cognitive Science

This article considers how connectionist modeling can contribute to understanding of human cognition. J argue that connectionist networks should not be thought of as theories or simulations of theories, but may nevertheless contribute to the development of theories.

A Developmental Deficit in Localizing Objects from Vision

We describe a college student, A H, with a developmental deficit in determining the location of objects from vision The deficit is selective in that (a) localization from auditory or tactile information is intact, (b) A H reports the identity of mislocalized objects accurately, (c) visual localization errors preserve certain parameters of the target location, and (d) visual localization is severely impaired under certain stimulus conditions, but nearly intact under other conditions These results bear on the representation and processing of location information in the visual system, and also have implications for understanding developmental dyslexia

Frontolimbic Morphometric Abnormalities in Intermittent Explosive Disorder and Aggression

BACKGROUND

Converging evidence from neuroimaging studies suggests that impulsive aggression, the core behavior in the DSM-5 diagnosis intermittent explosive disorder (IED), is regulated by frontolimbic brain structures, particularly orbitofrontal cortex, ventral medial prefrontal cortex, anterior cingulate cortex, amygdala, insula, and uncus. Despite this evidence, no brain volumetric studies of IED have been reported as yet. This study was conducted to test the hypothesis that gray matter volume in frontolimbic brain structures of subjects with IED is lower than in healthy subjects and subjects with other psychiatric conditions.

METHODS

High-resolution magnetic resonance imaging scans using a three-dimensional magnetization-prepared rapid acquisition gradient-echo sequence were performed in 168 subjects (n = 53 healthy control subjects, n = 58 psychiatric controls, n = 57 subjects with IED). Imaging data were analyzed by voxel-based morphometry methods employing Statistical Parametric Mapping (SPM8) software.

RESULTS

Gray matter volume was found to be significantly lower in subjects with IED compared with healthy control subjects and psychiatric controls in orbitofrontal cortex, ventral medial prefrontal cortex, anterior cingulate cortex, amygdala, insula, and uncus. These differences were not due to various confounding factors or to comorbidity with other disorders previously reported to have reduced gray matter volume. Gray matter volume in these areas was significantly and inversely correlated with measures of aggression.

CONCLUSIONS

Reductions in the gray matter volume of frontolimbic structures may be a neuronal characteristic of impulsively aggressive individuals with DSM-5 IED. These data suggest an anatomic correlate accounting for functional deficits in social-emotional information processing in these individuals.

Morphometric analysis of amygdla and hippocampus shape in impulsively aggressive and healthy control subjects

BACKGROUND

Impulsive aggressive behavior is thought to be facilitated by activation of the limbic brain, particularly the amygdala and hippocampus., Functional imaging studies suggest abnormalities in limbic brain activity during emotional information processing in impulsively aggressive subjects with Intermittent Explosive Disorder (IED). It is not known if IED is associated with altered amygdala and hippocampus volume and shape.

METHODS

We examined the volume and shape of the amygdala-hippocampal complex, using morphometric analysis of high resolution structural 3T MR scans in healthy control (HC: n = 73) subjects without history of Axis I or II psychiatric conditions and in subjects with IED (n = 67).

RESULTS

While no volume differences were observed between HC and IED subjects, a significant level of morphometric deformation, suggestive of cell loss, in both amygdala and hippocampal structures was observed bilaterally in IED subjects. Analysis of a canonical variable that used the first 10 eigenvectors from both sides of the brain revealed that these morphometric deformations in the IED subjects were not due the presence of confounding variables or to comorbidities among IED subjects.

CONCLUSIONS

These data reveal that IED is associated with a significant loss of neurons in both the amygdala and hippocampus. These changes may play a role in the functional abnormalities observed in previous fMRI studies and in the pathophysiology of impulsive aggressive behavior.

Criminal Behavior and Repeat Violent Trauma: A Case-Control Study

INTRODUCTION

Repeat violent injury is common among young urban men and is increasingly a focus of trauma center-based injury prevention efforts. Though understanding risk factors for repeat violent injury may be critical in designing such interventions, this knowledge is limited. This study aims to determine which criminal behaviors, both before and after the initial trauma, predict repeat violent trauma. Gun, violent, and drug crimes are expected to increase risk of subsequent violent injury among victims of violence.

METHODS

A case-control design examined trauma registry and publicly available criminal data for all male patients aged <40 years presenting for violent trauma between April 2006 and December 2011 (N=1,142) to the sole Level 1 trauma center in a city with high rates of violence. Logistic regression was used to determine criminal behaviors predictive of repeat violent injury. Data were obtained and analyzed between January 2013 and June 2014.

RESULTS

Regarding crimes committed before the first injury, only drug crime (OR=5.32) predicted repeat violent trauma. With respect to crimes committed after the initial injury, illegal gun possession (OR=2.70) predicted repeat victimization. Initiating gun (OR=3.53) or drug crime (OR=5.12) was associated with increased risk.

CONCLUSIONS

Prior drug involvement may identify young male victims of violence as at high risk of repeat violent injury. Gun carrying and initiating drug involvement after the initial injury may increase risk of repeat injury and may be important targets for interventions aimed at preventing repeat violent trauma.

A deficit perceiving slow motion after brain damage and a parallel deficit induced by crowding

Motion perception is known to involve at least 2 kinds of mechanisms-lower level signal detectors and higher level algorithms for comparing object positions over time. When stimulus motion is modal (continuously visible), it is generally assumed that processing via lower level mechanisms is sufficient to make accurate motion judgments. We investigated the possibility that higher level mechanisms may also be involved in the processing of slow motion, even when it is smooth and continuous. This possibility was suggested by results from a brain-damaged patient, JKI, who showed left visual field deficits in both the explicit representation of object position and judgments concerning the direction of slow, but not fast, smooth motion. We investigated the possibility further by using crowding to induce a behaviorally similar motion-perception deficit in healthy observers. Crowding, which is known to impair object-position representation, impaired direction judgments for slow, but not for faster, smooth motion. The results suggest an everyday role for higher level mechanisms in the perception of slow motion, and they reinforce the taxonomy of motion perception in terms of underlying processing mechanisms as opposed to stimulus properties.

Severity of vision loss interacts with word-specific features to impact out-loud reading in glaucoma

PURPOSE

To assess the impact of glaucoma-related vision loss on measures of out-loud reading, including time to say individual words, interval time between consecutive words, lexical errors, skipped words, and repetitions.

METHODS

Glaucoma subjects (n = 63) with bilateral visual field loss and glaucoma suspect controls (n = 57) were recorded while reading a standardized passage out loud. A masked evaluator determined the start and end of each recorded word and identified reading errors.

RESULTS

Glaucoma subjects demonstrated longer durations to recite individual words (265 vs. 243 ms, P < 0.001), longer intervals between words (154 vs. 124 ms, P < 0.001), and longer word/post-word interval complexes (the time spanned by the word and the interval following the word; 419 vs. 367 ms, P < 0.001) than controls. In multivariable analyses, each 0.1 decrement in log contrast sensitivity (logCS) was associated with a 15.0 ms longer word/post-interval complex (95% confidence interval [CI] = 9.6-20.4; P < 0.001). Contrast sensitivity was found to significantly interact with word length, word frequency, and word location at the end of a line with regards to word/post-word interval complex duration (P < 0.05 for all). Glaucoma severity was also associated with more lexical errors (Odds ratio = 1.20 for every 0.1 logCS decrement; 95% CI = 1.02-1.39, P < 0.05), but not with more skipped or repeated words.

CONCLUSIONS

Glaucoma patients with greater vision loss make more lexical errors, are slower in reciting longer and less frequently used words, and more slowly transition to new lines of text. These problem areas may require special attention when designing methods to rehabilitate reading in patients with glaucoma.

Representation of item position in immediate serial recall: Evidence from intrusion errors

In immediate serial recall, participants are asked to recall novel sequences of items in the correct order. Theories of the representations and processes required for this task differ in how order information is maintained; some have argued that order is represented through item-to-item associations, while others have argued that each item is coded for its position in a sequence, with position being defined either by distance from the start of the sequence, or by distance from both the start and the end of the sequence. Previous researchers have used error analyses to adjudicate between these different proposals. However, these previous attempts have not allowed researchers to examine the full set of alternative proposals. In the current study, we analyzed errors produced in 2 immediate serial recall experiments that differ in the modality of input (visual vs. aural presentation of words) and the modality of output (typed vs. spoken responses), using new analysis methods that allow for a greater number of alternative hypotheses to be considered. We find evidence that sequence positions are represented relative to both the start and the end of the sequence, and show a contribution of the end-based representation beyond the final item in the sequence. We also find limited evidence for item-to-item associations, suggesting that both a start-end positional scheme and item-to-item associations play a role in representing item order in immediate serial recall.

Severity of Vision Loss Interacts with Word-Specific Features to Impact Out-Loud Reading in Glaucoma

Purpose: To assess the impact of glaucoma-related vision loss on measures of out-loud reading, including time to say individual words, interval time between consecutive words, lexical errors, skipped words, and repetitions. Methods: Glaucoma subjects (n=63) with bilateral visual field loss and glaucoma suspect controls (n=57) were recorded while reading a standardized passage out loud. A masked evaluator determined the start and end of each recorded word and identified reading errors. Results: Glaucoma subjects demonstrated longer durations to recite individual words (265 vs 243 milliseconds (ms), p<0.001), longer intervals between words (154 vs 124 ms, p<0.001), and longer word/post-word interval complexes (the time spanned by the word and the interval following the word) (419 vs. 367 ms, p<0.001) than controls. In multivariable analyses, each 0.1 decrement in log contrast sensitivity (logCS) was associated with a 15.0 ms longer word/post-interval complex (95% CI=9.6-20.4; p<0.001). Contrast sensitivity was found to significantly interact with word length, word frequency, and word location at the end of a line with regards to word/post-word interval complex duration (p<0.05 for all). Glaucoma severity was also associated with more lexical errors (Odds ratio=1.20 for every 0.1 logCS decrement; 95% CI=1.02-1.39, p<0.05), but not with more skipped or repeated words. Conclusions: Glaucoma patients with greater vision loss make more lexical errors, are slower in reciting longer and less frequently used words, and more slowly transition to new lines of text. These problem areas may require special attention when designing methods to rehabilitate reading in patients with glaucoma.

Somatotopic representation of location: evidence from the Simon effect

Representing the locations of tactile stimulation can involve somatotopic reference frames in which locations are defined relative to a position on the skin surface, and also external reference frames that take into account stimulus position in external space. Locations in somatotopic and external reference frames can conflict in terms of left/right assignment when the hands are crossed or positioned outside of their typical hemispace. To investigate the spatial codes of the representation of both tactile stimuli and responses to touch, a Simon effect task, often used in the visual modality to examine issues of spatial reference frames, was deployed in the tactile modality. Participants performed the task with stimuli delivered to the hands with arms in crossed or uncrossed postures and responses were produced with foot pedals. Across all 4 experiments, participants were faster on somatotopically congruent trials (e.g., left hand stimulus, left foot response) than on somatotopically incongruent trials (left hand stimulus, right foot response), regardless of arm or leg position. However, some evidence of an externally based Simon effect also appeared in 1 experiment in which arm (stimulus) and leg (response) position were both manipulated. Overall, the results demonstrate that tactile stimulus and response codes are primarily generated based on their somatotopic identity. However, stimulus and response coding based on an external reference frame can become more salient when both hands and feet can be crossed, creating a situation in which somatotopic and external representations can differ for both stimulus and response codes.

New learning of music after bilateral medial temporal lobe damage: evidence from an amnesic patient

Damage to the hippocampus impairs the ability to acquire new declarative memories, but not the ability to learn simple motor tasks. An unresolved question is whether hippocampal damage affects learning for music performance, which requires motor processes, but in a cognitively complex context. We studied learning of novel musical pieces by sight-reading in a newly identified amnesic, LSJ, who was a skilled amateur violist prior to contracting herpes simplex encephalitis. LSJ has suffered virtually complete destruction of the hippocampus bilaterally, as well as extensive damage to other medial temporal lobe structures and the left anterior temporal lobe. Because of LSJ's rare combination of musical training and near-complete hippocampal destruction, her case provides a unique opportunity to investigate the role of the hippocampus for complex motor learning processes specifically related to music performance. Three novel pieces of viola music were composed and closely matched for factors contributing to a piece's musical complexity. LSJ practiced playing two of the pieces, one in each of the two sessions during the same day. Relative to a third unpracticed control piece, LSJ showed significant pre- to post-training improvement for the two practiced pieces. Learning effects were observed both with detailed analyses of correctly played notes, and with subjective whole-piece performance evaluations by string instrument players. The learning effects were evident immediately after practice and 14 days later. The observed learning stands in sharp contrast to LSJ's complete lack of awareness that the same pieces were being presented repeatedly, and to the profound impairments she exhibits in other learning tasks. Although learning in simple motor tasks has been previously observed in amnesic patients, our results demonstrate that non-hippocampal structures can support complex learning of novel musical sequences for music performance.

Profound loss of general knowledge in retrograde amnesia: evidence from an amnesic artist

Studies of retrograde amnesia have focused on autobiographical memory, with fewer studies examining how non-autobiographical memory is affected. Those that have done so have focused primarily on memory for famous people and public events—relatively limited aspects of memory that are tied to learning during specific times of life and do not deeply tap into the rich and extensive knowledge structures that are developed over a lifetime. To assess whether retrograde amnesia can also cause impairments to other forms of general world knowledge, we explored losses across a broad range of knowledge domains in a newly-identified amnesic. LSJ is a professional artist, amateur musician and history buff with extensive bilateral medial temporal and left anterior temporal damage. We examined LSJ's knowledge across a range of everyday domains (e.g., sports) and domains for which she had premorbid expertise (e.g., famous paintings). Across all domains tested, LSJ showed losses of knowledge at a level of breadth and depth never before documented in retrograde amnesia. These results show that retrograde amnesia can involve broad and deep deficits across a range of general world knowledge domains. Thus, losses that have already been well-documented (famous people and public events) may severely underestimate the nature of human knowledge impairment that can occur in retrograde amnesia.

Representation of letter position in single-word reading: evidence from acquired dyslexia

Visual word recognition requires information about the positions as well as the identities of the letters in a word. This study addresses representation of letter position at prelexical levels of the word recognition process. We present evidence from an acquired dyslexic patient, L.H.D., who perseverates letters in single-word reading tasks: Far more often than expected by chance, L.H.D.'s reading responses include letters from preceding responses (e.g., SAILOR read as SAILOG immediately after FLAG was read correctly). Analyses carried out over two large data sets compared the positions of perseverated letters (e.g., the G in SAILOG) with the positions of the corresponding "source" letters (e.g., the G in FLAG). The analyses assessed the extent to which the perseverations preserved source position as defined by various theories of letter position representation. The results provided strong evidence for graded both-edges position representations, in which the position of each letter is encoded coarsely relative to both the beginning and the end of the word. Alternative position representation schemes, including letter-context and orthosyllabic schemes, were not supported.

Prelexical representations and processes in reading: evidence from acquired dyslexia

We report a detailed and extensive single-case study of an acquired dyslexic patient, L.H.D., who suffered a left-hemisphere lesion as a result of a ruptured aneurysm. We present evidence that L.H.D.'s reading errors stem from a deficit in visual letter identification, and we use her deficit as a basis for exploring a variety of issues concerning prelexical representations and processes in reading. First, building on the work of other researchers, we present evidence that the prelexical reading system includes an allograph level of representation that represents each distinct visual shape of a letter (e.g., a, A, etc., for the letter A). We extend a theory proposed by Caramazza and Hillis [Caramazza, A., & Hillis, A. (1990a). Spatial representation of words in the brain implied by studies of a unilateral neglect patient. Nature, 346, 267-269] to include an allograph level, and we probe the nature of the allograph representations in some detail. Next, we explore the implications of visual similarity effects and letter perseverations in L.H.D.'s reading performance, arguing that these effects shed light on activation dynamics in the prelexical reading system and on the genesis of L.H.D.'s errors. We also probe the processing of letter case in the visual letter identification process, proposing that separate abstract letter identity and case representations are computed. Finally, we present evidence that the allograph level as well as the abstract letter identity level implement a word-based frame of reference.

The necessity of the medial temporal lobe for statistical learning

The sensory input that we experience is highly patterned, and we are experts at detecting these regularities. Although the extraction of such regularities, or statistical learning (SL), is typically viewed as a cortical process, recent studies have implicated the medial temporal lobe (MTL), including the hippocampus. These studies have employed fMRI, leaving open the possibility that the MTL is involved but not necessary for SL. Here, we examined this issue in a case study of LSJ, a patient with complete bilateral hippocampal loss and broader MTL damage. In Experiments 1 and 2, LSJ and matched control participants were passively exposed to a continuous sequence of shapes, syllables, scenes, or tones containing temporal regularities in the co-occurrence of items. In a subsequent test phase, the control groups exhibited reliable SL in all conditions, successfully discriminating regularities from recombinations of the same items into novel foil sequences. LSJ, however, exhibited no SL, failing to discriminate regularities from foils. Experiment 3 ruled out more general explanations for this failure, such as inattention during exposure or difficulty following test instructions, by showing that LSJ could discriminate which individual items had been exposed. These findings provide converging support for the importance of the MTL in extracting temporal regularities.