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Julie A Fiez

Publications and source records attributed to Julie A Fiez.

15 recordsLinked to original sources
PubMed2006

Specific reading and phonological processing deficits are associated with damage to the left frontal operculum.

Functional neuroimaging studies in normal subjects indicate that a region in the left frontal operculum (FO) is more active when subjects read pronounceable nonwords as compared to most word types. Here, we report convergent evidence on this finding using the lesion method. We tested the prediction that subjects with left FO damage would have impaired reading of pronounceable nonwords, but relatively intact reading of most word types. Eleven target subjects with circumscribed left FO lesions, and two comparison groups of either brain-damaged or normal subjects matched to the target subjects for age, sex, handedness, and education, were studied using reading tasks derived from previous neuroimaging work. As predicted, the FO group was significantly less accurate than the comparison groups at reading nonwords. By contrast, the FO subjects showed relatively intact word reading, a pattern consistent with the syndrome of "phonological dyslexia". The FO subjects, however, did exhibit particular difficulty reading low frequency words with inconsistent grapheme-to-phoneme correspondences (e.g., PINT), which parallels the finding from functional imaging studies that reading such items produces more activation in left FO than reading high frequency words and low frequency words with consistent grapheme-to-phoneme correspondences (e.g., JADE) (Fiez et al., 1999). In several follow-up experiments, we found that the FO subjects were also impaired on other phonological tasks that have been associated with left frontal opercular activation in functional neuroimaging studies. The findings converge nicely with extant functional imaging work, and provide further evidence that regions within the left FO are part of a system that makes specific and critical contributions to some of the phonological processes that support reading.

Adult↗
PubMed2006

Performance feedback drives caudate activation in a phonological learning task.

Adults have difficulty discriminating nonnative phonetic contrasts, but under certain circumstances training can lead to improvement in this ability. Despite the ubiquitous use of performance feedback in training paradigms in this and many other domains, the mechanisms by which feedback affects learning are not well understood. In this event-related functional magnetic resonance imaging study, we examined how performance feedback is processed during perceptual learning. Thirteen Japanese speakers for whom the English phonemes [r] and [l] were nondistinct performed an identification task of the words "road" and "load" that has been shown to be effective in inducing learning only when performance feedback is present. Each subject performed alternating runs of training with and without feedback, followed by performance of a card-guessing task with monetary reward and punishment outcomes. We found that the caudate nucleus was more robustly activated bilaterally when performing the perceptual identification task with feedback than without feedback, and the right caudate nucleus also showed a differential response to positive and negative feedback. Moreover, using a within-subjects design, we found that the caudate nucleus also showed a similar activation pattern to monetary reward and punishment outcomes in the card-guessing task. These results demonstrate that the caudate responds to positive and negative feedback during learning in a manner analogous to its processing of extrinsic affective reinforcers and indicate that this region may be a critical moderator of the influence of feedback on learning. These findings impact our broader understanding of the mechanisms underlying nondeclarative learning and language acquisition.

Adult↗
PubMed2005

Cerebellar damage produces selective deficits in verbal working memory.

The cerebellum is often active in imaging studies of verbal working memory, consistent with a putative role in articulatory rehearsal. While patients with cerebellar damage occasionally exhibit a mild impairment on standard neuropsychological tests of working memory, these tests are not diagnostic for exploring these processes in detail. The current study was designed to determine whether damage to the cerebellum is associated with impairments on a range of verbal working memory tasks, and if so, under what circumstances. Moreover, we assessed the hypothesis that these impairments are related to impaired rehearsal mechanisms. Patients with damage to the cerebellum (n = 15) exhibited a selective deficit in verbal working memory: spatial forward and backward spans were normal, but forward and backward verbal spans were lower than controls. While the differences were significant, digit spans were relatively preserved, especially in comparison to the dramatic reductions typically observed in classic 'short-term memory' patients with perisylvian brain damage. The patients tended to be more impaired on a verbal version compared to a spatial version of a working memory task with a long delay and this impairment was correlated with overall symptom and dysarthria severity. These results are consistent with a contribution of the cerebellum to rehearsal and suggest that inclusion of a delay before recall is especially detrimental in individuals with cerebellar damage. However, when we examined markers of rehearsal (i.e. word-length and articulatory suppression effects) in an immediate serial recall task, we found that qualitative aspects of the patients' rehearsal strategies were unaffected. We propose that the cerebellum may contribute to verbal working memory during the initial phonological encoding and/or by strengthening memory traces rather than by fundamentally subserving covert articulatory rehearsal.

Adult↗
PubMed2005

Right parietal contributions to verbal working memory: spatial or executive?

The left inferior parietal cortex has been claimed to be the site of the verbal short-term store, yet imaging studies report activity of a homologous right-hemisphere region in verbal working memory tasks as well. In spite of its prevalent activity, right parietal contributions to verbal working memory are poorly understood. To clarify its role in verbal working memory performance, we tested a patient with a lesion in the right parietal lobe on verbal and spatial versions of the N-back task. The patient was impaired in all the spatial conditions regardless of load (0-, 1-, and 2-back), whereas in the verbal N-back he was impaired only in the conditions with a memory demand (1- and 2-back). Given that we had presented stimuli at multiple locations in the verbal N-back, however, it remained possible that the lesion impaired spatial representation rather than verbal working memory per se. With central stimulus presentation, his performance dramatically improved indicating that his difficulty with the N-back task was largely due to his poor visuospatial abilities.

Aged↗
PubMed2005

Reduced phonological similarity effects in patients with damage to the cerebellum.

Ten cerebellar patients were compared to 10 control subjects on a verbal working memory task in which the phonological similarity of the words to be remembered and their modality of presentation were manipulated. Cerebellar patients demonstrated a reduction of the phonological similarity effect relative to controls. Further, this reduction did not depend systematically upon the presentation modality. These results first document that qualitative differences in verbal working memory may be observed following cerebellar damage, indicating altered cognitive processing, even though behavioral output as measured by the digit span may be within normal limits. However, the results also present problems for the hypothesis that the cerebellar role is specifically associated with articulatory rehearsal as conceptualized in the Baddeley-Hitch model of working memory.

Acoustic Stimulation↗
PubMed2005

Instructed smoking expectancy modulates cue-elicited neural activity: a preliminary study.

In recent years, research applying functional neuroimaging to the study of cue-elicited drug craving has emerged. This research has begun to identify a distributed system of brain activity during drug craving. A review of this literature suggested that expectations regarding the opportunity to use a drug affected the pattern of neural responses elicited by drug cues. Using functional magnetic resonance imaging (fMRI), we examined the effects of smoking expectancy on the neural response to neutral (e.g., roll of tape) and smoking-related (a cigarette) stimuli in male cigarette smokers deprived of nicotine for 8 hr. As predicted, several brain regions (e.g., the anterior cingulate cortex) exhibited differential activation during cigarette versus neutral cue exposure. Moreover, we found that subregions of the prefrontal cortex (i.e., ventromedial, ventrolateral, and dorsolateral prefrontal cortices) showed cue-elicited activation that was modulated by smoking expectancy. These results highlight the importance of perceived drug use opportunity in the neurobiological response to drug cues.

Adult↗
PubMed2004

Prefrontal responses to drug cues: a neurocognitive analysis.

The construct of craving has been central to addiction research for more than 50 years. Only recently have investigators begun to apply functional neuroimaging techniques to the study of drug cue reactivity, and a small but growing number of studies implicate a distributed system of brain regions in the pathogenesis of craving. The internal consistency of this burgeoning literature has thus far been disappointing, however, leaving open the question of which brain regions contribute to craving. Here we review neuroimaging studies of cue-elicited craving in the context of a framework drawn from behavioral research indicating that perceived drug use opportunity significantly affects responses to the presentation of drug cues. Using this framework provides a way to reconcile discrepant findings among brain-imaging studies of cue-elicited craving.

Amygdala↗
PubMed2004

Event-related functional magnetic resonance imaging of reward-related brain circuitry in children and adolescents.

BACKGROUND: Functional disturbances in reward-related brain systems are thought to play a role in the development of mood, impulse, and substance-abuse disorders. Studies in nonhuman primates have identified brain regions, including the dorsal/ventral striatum and orbital-frontal cortex, in which neural activity is modulated by reward. Recent studies in adults have concurred with these findings by observing reward-contingent blood oxygen level-dependent (BOLD) responses in these regions during functional magnetic resonance imaging (fMRI) paradigms; however, no previous studies indicate whether comparable modulations of neural activity exist in the brain reward systems of children and adolescents. METHODS: We used event-related fMRI and a behavioral paradigm modeled on previous work in adults to study brain responses to monetary gains and losses in psychiatrically healthy children and adolescents as part of a program examining the neural substrates of anxiety and depression in youth. RESULTS: Regions and time-courses of reward-related activity were similar to those observed in adults with condition-dependent BOLD changes in the ventral striatum and lateral and medial orbital-frontal cortex; specifically, these regions showed larger responses to positive than to negative feedback. CONCLUSIONS: These results provide further evidence for the value of event-related fMRI in examining reward systems of the brain, demonstrate the feasibility of this approach in children and adolescents, and establish a baseline from which to understand the pathophysiology of reward-related psychiatric disorders in youth.

Adolescent↗
PubMed2004

Modulation of caudate activity by action contingency.

Research has increasingly implicated the striatum in the processing of reward-related information in both animals and humans. However, it is unclear whether human striatal activation is driven solely by the hedonic properties of rewards or whether such activation is reliant on other factors, such as anticipation of upcoming reward or performance of an action to earn a reward. We used event-related functional magnetic resonance imaging to investigate hemodynamic responses to monetary rewards and punishments in three experiments that made use of an oddball paradigm. We presented reward and punishment displays randomly in time, following an anticipatory cue, or following a button press response. Robust and differential activation of the caudate nucleus occurred only when a perception of contingency existed between the button press response and the outcome. This finding suggests that the caudate is involved in reinforcement of action potentially leading to reward, rather than in processing reward per se.

Adult↗
PubMed2004

Functional dissociations within the inferior parietal cortex in verbal working memory.

Neuroimaging studies of working memory have revealed two sites in the left supramarginal gyrus that may support the short-term storage of phonological information. Activation in the left dorsal aspect of the inferior parietal cortex (DIPC) has been observed in contrasts of working memory load, whereas activation in the ventral aspect of the inferior parietal cortex (VIPC) has been found primarily in contrast of information type (verbal vs. nonverbal). Our goal was to determine whether these two areas are functionally distinct or if instead they are part of a homogeneous region with large variations in the focus of peak activity. Toward this end, we used fMRI to assess the neural response in two working memory tasks (N-back and item recognition) in which we also manipulated memory load and the type of information to be recalled (verbal vs. nonverbal). We found both DIPC and VIPC activation in the same group of subjects and further demonstrated that they have differential sensitivity to our experimental factors. Only the DIPC showed robust load effects, whereas only the VIPC showed reliable effects of information type. These results help to account for the differences observed in between-subject comparisons, and they indicate that the two regions are functionally dissociable. In contrast to the DIPC, activity of the VIPC was also recruited in the fixation and low-load conditions, a surprising result that has not been fully explored in prior studies. Despite their distinctive patterns of performance, neither of these regions displayed a pattern of activity that entirely corresponds to common assumptions of a dedicated phonological short-term store (STS). Instead, we hypothesize that the DIPC may support domain-general executive processes, while the VIPC may support phonological encoding-recoding processes central to a variety of language tasks.

Adult↗
PubMed2004

Integrating rewards and cognition in the frontal cortex.

Research indicates that the dorsolateral prefrontal cortex (DLPFC) contributes to working memory and executive control, whereas the ventral frontal cortex (VFC) contributes to affective and motivational processing. Few studies have examined both the functional specificity and the integration of these regions. We did so using fMRI and a verbal working memory task in which visual cues indicated whether recall performance on an upcoming trial would be linked to a monetary reward. On the basis of prior findings obtained in delayed response tasks performed by nonhuman primates, we hypothesized that (1) VFC would show an increase only in response to a cue indicating potential for a monetary reward; (2) DLPFC would show sustained activity across a delay interval for all trials, though activity in rewarded trials would be enhanced; and (3) regions engaged in speech-based rehearsal would be relatively insensitive to monetary incentive. Our hypotheses about DLPFC and rehearsal-related regions were confirmed. In VFC regions, we failed to observe statistically significant effects of reward when the cue or delay epochs of the task were examined in isolation. However, an unexpected and significant deactivation was observed in VFC during the delay epoch; furthermore, a post hoc voxelwise analysis indicated a complex interaction between (1) the cue and delay epochs of the task and (2) the reward value of the trials. The pattern of activation and deactivation across trial types suggests that VFC is sensitive to reward cues, and that portions of DLPFC and VFC may work in opposition during the delay epoch of a working memory task in order to facilitate task performance.

Adolescent↗
PubMed2002

Teaching the /r/-/l/ discrimination to Japanese adults: behavioral and neural aspects.

Several studies have been conducted to address the learning of a nonnative speech contrast in adulthood, using native speakers of Japanese and the English /r/-/l/ contrast. Japanese adults were asked to identify contrasting /r/-/l/ stimuli (e.g., "rock-lock"). An adaptive training regime starting with initially easy stimuli was contrasted with a fixed training regime using difficult stimuli, with some subjects receiving feedback on the correctness of their responses and others receiving no feedback in both conditions. After three and six sessions of training, subjects received tests assessing identification and discrimination of /r/-/l/ stimuli as well as generalization. In all cases except fixed training without feedback, subjects showed clear evidence of learning, and several indicators suggested that training affects speech perception, rather than simply auditory processes. Neuroimaging studies currently underway are examining the neural basis of these findings.

Behavior↗
PubMed2002

The phonological-similarity effect differentiates between two working memory tasks.

Working memory is a set of interactive cognitive processes that maintain information on-line and available for analysis. Part of the system is specialized for maintaining verbal information, a core component of which is thought to be a phonological store. On the basis of the study of patients with acquired brain lesions, this store has been localized to the supramarginal and angular gyri of the speech-dominant hemisphere, and some functional neuroimaging studies support this localization. However, other imaging studies localize the phonological store in a more dorsal region of the parietal lobe. To reconcile these findings, we examined the phonological-similarity effect in two different tasks. A phonological-similarity effect was observed only in the task that involved sequential presentation and explicit verbal rehearsal. We conclude that at least one possible source of the differences in brain activation between different working memory tasks may be differences in phonological processing.

Adult↗
PubMed2002

Success and failure in teaching the [r]-[l] contrast to Japanese adults: tests of a Hebbian model of plasticity and stabilization in spoken language perception.

A Hebbian model of learning predicts that adults may be able to acquire a nonnative speech contrast if they are trained with stimuli that are exaggerated to make them perceptually distinct. To test these ideas, we asked Japanese adults to identify contrasting [r]-[l] stimuli (e.g., rock-lock) in two training conditions. In the adaptive condition, the [r]-[l] contrast was exaggerated at first and then adjusted to maintain accurate identification. In the fixed condition, a fixed pair of stimuli were used that were distinguishable by native English speakers but difficult for the Japanese learners to discriminate. To examine whether feedback contributes to learning, we ran separate groups with and without feedback in the fixed and the adaptive conditions. Without feedback, 3 days of adaptive training produced substantial improvements, but 3 days of fixed training produced no benefit relative to control, consistent with the Hebbian account. With feedback, both fixed and adaptive training led to robust improvements, and the benefit of training transferred to a second continuum (e.g., road-load). The results are consistent with Hebbian models that are augmented to be sensitive to feedback.

Adult↗