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John F Connolly

Publications and source records attributed to John F Connolly.

18 recordsLinked to original sources
PubMed2006

Correlating digit span performance and event-related potentials to assess working memory.

Event-related brain potentials (ERPs) were recorded during a computerized and modified version of the Digit Span Backwards (DB) task from the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III). The modified DB version (ERP-DB task) was divided into two sections of 2, 4, 6 and 8 digits in length (Group 1) and 3, 5 and 7 digits in length (Group 2). Each trial had a study phase and a test phase. For the study phase, a series of digits was presented sequentially and aurally to 20 participants (10 for each group). For the test phase, a second series of digits was also presented sequentially and aurally that either corresponded to the reverse order of the digits in the study phase (correct condition) or had one digit in the sequence replaced by an incorrect digit (incorrect condition). The traditional DB task of the WAIS-III was also administered for comparison purposes. A prolonged positive slow wave (PSW) peaking between 450 and 750 ms was elicited to incorrect condition trials. For each participant, a derived measure was calculated from the ERP differentiation between correct and incorrect conditions. The derived measure was defined as the mean of the t-values obtained from the correct and incorrect waveform comparison, within the temporal interval that encompassed this component. The strongest statistical correlations between the derived measure and the traditional DB test scores were found at the Pz site (Group 1: r=0.79; Group 2: r=0.59). This statistical approach shows that it is possible to adequately relate an individual's performance on a traditional measure of working memory and ERP patterns. Overall, we believe that this kind of ERP approach holds promise as a technique for assessing quantitatively non-communicative patients.

Adult↗
PubMed2005

Assessment of working memory abilities using an event-related brain potential (ERP)-compatible digit span backward task.

OBJECTIVE: This study investigated the effectiveness of an ERP-compatible Digit Span Backward (ERP-DB) task to determine working memory abilities in healthy participants. METHODS: Participants were administered both the standard digit span backward and ERP-DB tasks. The ERP-DB task was divided into two sections, consisting of 2, 4, 6 and 8 (Group 1) and 3, 5, and 7 (Group 2) set sizes. A set of digits was aurally presented, followed by a second set that either corresponded to the reverse order of the first set (correct condition) or had one digit in the sequence replaced by an incorrect digit (incorrect condition). RESULTS: Two posterior positive components were found to distinguish the two conditions; an earlier positive component (P200/P300) was elicited in the correct condition, whereas a comparatively robust and prolonged positive slow wave (PSW) was elicited in the incorrect condition. Furthermore, the PSW and the difference in PSW amplitude between incorrect and correct conditions (dPSW) dissipated as working memory load increased and were related to working memory capacity. CONCLUSIONS: The PSW, dPSW and P200/P300 components were found to be associated with working memory abilities and may have the potential to act as neurophysiological markers for the assessment of working memory capacity. SIGNIFICANCE: This research lends support for the utility of the ERP-DB task as a means of assessing working memory abilities, which may have implications for testing patients with expressive communication impairments.

Adult↗
PubMed2005

The influence of increased working memory load on semantic neural systems: a high-resolution event-related brain potential study.

The effects of working memory (WM) on the semantic N400 response were studied using high-resolution event-related brain potentials (ERPs). Participants were presented with semantically related sentence pairs and the terminal word congruence was varied in the second sentence. WM load was varied for the sentence pairs using a modified fan procedure [J.R. Anderson, Retrieval of propositional information from long-term memory. Cogn. Psychol., 6 (1974) 451-474; J.R. Anderson, A spreading activation theory of memory. J. Verbal Learn. Verbal Behav., 22 (1983) 261-295]. ERPs were recorded to the onset of the terminal word (Congruent and Incongruent) for sentence pairs at two levels of WM load (WML1 and WML2). Behavioral data analysis revealed that reaction times (RTs) increased as a function of WM load (i.e., the fan effect). Semantically incongruent words elicited an N400 response. Increased WM load reduced the congruency effect and, importantly, resulted in a significant delay in N400 peak latency (approximately 50 ms). Moreover, the latency delay was correlated with a neuropsychological measure of individual WM capacity. WM load effects on the N400 were interpreted as a result of competing activation in WM, both modulating semantic expectancies and delaying semantic integration. Exploratory source analysis revealed activation in occipital, temporal, and parietal regions. Consistent with prior reports on the N400 and semantic processing, equivalent current dipoles were modeled in the left perisylvian region. Increased WM load led to novel source activation in the left inferior parietal region as well as increased activation levels in anterior temporal sources. The source modeling results were in agreement with the functional roles typically ascribed to these areas and confirmed that the scalp-recorded WM load effects on the N400 were present within the intracranial generators.

Adult↗
PubMed2004

The fan effect in fMRI: left hemisphere specialization in verbal working memory.

We studied the fan effect of verbal working memory using functional magnetic resonance imaging (fMRI). Participants were presented with a sentence-pair matching task that described semantic relationships (e.g. classroom-school). Working memory load and semantic processing were manipulated by increasing the number of sentences to be remembered and varying whether they matched expectation. Increased working memory load elicited activation in left dorsal frontal and left inferior parietal regions, and also delayed the hemodynamic responses. Convergent results from semantic matches occurred in the left parietal lobe, whereas, left ventral frontal activation from mismatches diverged from working memory results. The findings were consistent with behavioural and electrophysiological evidence, with the fan effect in fMRI providing novel insight into the spatiotemporal nature of verbal working memory in the left hemisphere.

Adult↗
PubMed2004

Separating phonological and semantic processing in auditory sentence processing: a high-resolution event-related brain potential study.

Phonological and semantic processing was studied using high-resolution event-related brain potentials (ERPs) during a sentence-matching task to investigate the spatial distribution of the phonological mismatch negativity (PMN) and the N400 response. It was hypothesized that the two components were spatially separable and that the activity matched prior localization knowledge. Participants examined visual-auditory sentence pairs that related within a semantic hierarchy (e.g., visual: "The man is teaching in the classroom"; Auditory: "The man is in the em leader school/barn"). Semantic congruency was varied for the final words of the spoken sentences. Incongruent words mismatched expectation in terms of both the initial phonological features (unexpected sound) and semantic features (unexpected meaning). In addition, the category-exemplar probability of the final words was either high or low, with low probability words being more difficult to anticipate. Low probability words were predicted to selectively affect PMN activity. We found that incongruent words elicited a PMN (287 msec) and a N400 (424 msec), for both the high and low probability words. As expected, low probability congruent words elicited a small PMN but no N400. In contrast, high probability congruent words elicited neither a detectible PMN nor a N400. The primary PMN sources were in left inferior frontal and inferior parietal lobes. The primary N400 source activation occurred along the left perisylvian cortex, consistent with prior N400 source localization work. From these results, it was concluded that the PMN and N400 were localized to separate cortical language (and memory) regions and had different source activation patterns.

Adult↗
PubMed2004

Determining the role of phonology in silent reading using event-related brain potentials.

The goal of the present study was to delineate phonology's role in silent reading using event-related brain potential (ERP) techniques. Terminal endings of high cloze sentences were manipulated in four conditions in which the terminal word was: (1) the high cloze ending and thus orthographically, phonologically and semantically congruent (e.g., The gambler had a streak of bad luck.); (2) a pseudohomophone that was orthographically incongruent, but was phonologically congruent to the anticipated ending (e.g., The ship disappeared into the thick phog [fog].); (3) a word that was orthographically, phonologically and semantically incongruent to expectations (e.g., The dog chased the cat up the Queen [tree].); or (4) a nonword and consequently orthographically, phonologically and semantically incongruent to expectations (e.g., The gas station is about two miles down the bole [road].). A N270 was elicited by orthographically incongruent words and nonwords (conditions 2, 3 and 4), likely reflecting violations of orthographic form expectations, while the presence of the N400 to semantically incongruent words and nonwords (conditions 3 and 4) reflected violations of semantic expectations. The relative absence of the N400 response to pseudohomophones (condition 3) indicates that integrating word meaning with sentential context is influenced by the phonological representation of the presented letter string. The implication of these results for theories of word recognition is discussed.

Adult↗
PubMed2004

Activation in the anterior left auditory cortex associated with phonological analysis of speech input: localization of the phonological mismatch negativity response with MEG.

The spatio-temporal dynamics of cortical activation underlying auditory word recognition, particularly its phonological stage, was studied with whole-head magnetoencephalography (MEG). Subjects performed a visuo-auditory priming task known to evoke the phonological mismatch negativity (PMN) response that is elicited by violations of phonological expectancies. Words and non-words were presented in separate conditions. In each of the 318 trials, the subjects first saw a word/non-word (e.g., 'cat') that was soon followed by a prime letter (e.g., 'h'). Their task was to replace mentally the sound of the first letter of the word/non-word with the prime letter, thus resulting in a new word/non-word (e.g., 'hat'). Finally, an auditory word/non-word either matching or mismatching with the anticipated item was presented. In most subjects, a PMNm followed by a later, N400m-like negativity was obtained in the left hemisphere to the mismatching auditory stimuli. A similar response pattern was obtained in the right hemisphere only in a few subjects. Source localization of the N1m, an index of acoustic analysis, and the PMNm and N400m-like responses was performed using L1 minimum-norm estimation. In the left hemisphere, the PMNm source for the words was significantly more anterior than the source of the N400m-like response; for the non-words, the PMNm source was significantly more anterior than the sources of the N1m and the N400m-like response. These results suggest that the left-hemisphere neuronal networks involved in sub-lexical phonological analysis are at least partly different from those responsible for the earlier (acoustic) and later (whole item) processing of speech input.

Acoustic Stimulation↗
PubMed2004

Assessing the effect of pain on demands for attentional resources using ERPs.

Event-related potentials were used as an adjunct to behavioral and self-report measures to examine the impact of pain in a short-term memory-scanning task. P3 amplitude was reduced and a frontal slow wave was increased during pain regardless of the number of items in memory. Results are discussed in terms of pain affecting an attention-switch mechanism.

Adolescent↗
PubMed2004

Prognostic value of evoked responses and event-related brain potentials in coma.

The behaviourally unresponsive patient, unable to exhibit the presence of cognition, constitutes a conundrum for health care specialists. Prognostic uncertainty impedes accurate management decisions and the application of ethical principles. An early, reliable prognosis is highly desirable. In this review investigations studying comatose patients with coma of different etiologies were selected. It is concluded that objective prognostication is enhanced by the use of electrophysiological tests. Persistent abnormalities of brainstem auditory evoked potentials and short-latency somatosensory evoked potentials reliably indicate the likelihood of irreversible neurological deficit or death. Meanwhile, the presence of "cognitive" event-related brain potentials (e.g., P300 and mismatch negativity) reflects the functional integrity of higher level information processing and, therefore, the likelihood of capacity for cognition. An approach that combines clinical and electrophysiological values provides optimal prediction of outcome and level of disability.

Acoustic Stimulation↗
PubMed2003

Comparison of bone grafts for posterior spinal fusion in adolescent idiopathic scoliosis.

STUDY DESIGN: A retrospective comparison of three different types of bone grafts for posterior spinal fusion in adolescent idiopathic scoliosis. OBJECTIVE: To determine the efficacy of bone marrow and demineralized bone matrix as a bone graft substitute for spinal fusion. SUMMARY OF BACKGROUND DATA: Several reports have documented a high morbidity associated with harvesting autologous iliac crest bone graft (ICBG) for spinal fusion. Composite bone graft consisting of demineralized bone matrix and aspirated bone marrow may reduce the morbidity and still retain the osteoinductive properties of iliac crest autograft. METHODS: Three different bone grafting techniques were used by a single surgeon in 88 consecutive patients who had posterior spinal fusion for adolescent idiopathic scoliosis. Segmental instrumentation with dual-rod fixation was used in all cases. Selection of type of graft was determined historically by the time when the operations were performed. Autologous ICBG was used in Group A, freeze-dried corticocancellous allograft in Group B, and composite graft of autologous bone marrow and demineralized bone matrix in Group C. Seventy-seven patients were reviewed, with a minimum of 2 years' follow-up (mean, 3 years 7 months; range, 2 years-9 years 5 months). Radiographs were assessed for pseudarthrosis and loss of correction of 10 degrees or more. Loss of 10 degrees of correction has been previously identified as an indicator of potential pseudarthrosis or fusion instability. Both of these criteria were used to compare success of fusion. RESULTS: Failure caused by pseudarthroses was seen in two patients (2.6%), one in Group A and one in Group B. Eleven patients lost greater than 10 degrees of correction, but only one demonstrated pseudarthroses. The 13 patients with pseudarthroses or loss of correction constitute the failure group for purposes of graft assessment. The failure rate was 12.5% in Group A (ICBG), 28% in Group B (freeze-dried corticocancellous allograft), and 11.1% in Group C (composite graft of autologous bone marrow and demineralized bone matrix). Eliminating patients with crankshaft phenomenon did not substantially change the results. There was no morbidity associated with bone marrow aspiration. CONCLUSIONS: Fusion rates were comparable for GroupA (ICBG) and Group C (composite graft of autologous bone marrow and demineralized bone matrix). The composite graft is our preferred graft for fusions in adolescent idiopathic scoliosis.

Adolescent↗
PubMed2003

Electrophysiological assessment of language function following stroke.

OBJECTIVE: Event-related brain potentials (ERPs) were used to assess language function after stroke and demonstrate that it is possible to adapt neuropsychological tests to evaluate neurocognitive function using ERPs. Prior ERP assessment work has focused on language in both healthy individuals and case studies of aphasic neurotrauma patients. The objective of the current study was to evaluate left-hemisphere stroke patients who had varying degrees of receptive language impairment. It was hypothesized that ERPs would assess receptive language function accurately and correlate highly with the neuropsychological data. METHODS: Data were collected from 10 left-hemisphere stroke patients; all were undergoing rehabilitation at the time of testing. Each patient received a battery of neuropsychological tests including the Peabody Picture Vocabulary Test-Revised (PPVT-R; Minnesota: American Guidance Service, 1981). ERPs were recorded during a computerized PPVT-R, in which pictures are presented followed by digitized spoken words that are either congruent or incongruent with the pictures. RESULTS AND CONCLUSION: Incongruent spoken words within an individual's vocabulary level elicited well-known ERP components. One of the components (the N400) could be utilized as a marker of intact semantic processing. The ERP results were subsequently quantified and N400 derivative scores correlated highly with the neuropsychological findings. The results provided a clear demonstration of the efficacy of ERP-based assessment in a neurological patient group. SIGNIFICANCE: Language function in stroke patients can be evaluated, independent of behavior, using electrophysiological measures that correlate highly with traditional neuropsychological test scores.

Acoustic Stimulation↗
PubMed2002

Cortical activation during spoken-word segmentation in nonreading-impaired and dyslexic adults.

We used magnetoencephalography to elucidate the cortical activation associated with the segmentation of spoken words in nonreading-impaired and dyslexic adults. The subjects listened to binaurally presented sentences where the sentence-ending words were either semantically appropriate or inappropriate to the preceding sentence context. Half of the inappropriate final words shared two or three initial phonemes with the highly expected semantically appropriate words. Two temporally and functionally distinct response patterns were detected in the superior temporal lobe. The first response peaked at approximately 100 msec in the supratemporal plane and showed no sensitivity to the semantic appropriateness of the final word. This presemantic N100m response was abnormally strong in the left hemisphere of dyslexic individuals. After the N100m response, the semantically inappropriate sentence-ending words evoked stronger activation than the expected endings in the superior temporal cortex in the vicinity of the auditory cortex. This N400m response was delayed for words starting with the same two or three first few phonemes as the expected words but only until the first evidence of acoustic-phonetic dissimilarity emerged. This subtle delay supports the notion of initial lexical access being based on phonemes or acoustic features. In dyslexic participants, this qualitative aspect of word processing appeared to be normal. However, for all words alike, the ascending slope of the semantic activation in the left hemisphere was delayed by approximately 50 msec as compared with control subjects. The delay in the auditory N400m response in dyslexic subjects is likely to result from presemantic-phonological deficits possibly reflected in the abnormal N100m response.

Acoustic Stimulation↗
PubMed2002

Linking neurophysiological and neuropsychological measures for aphasia assessment.

OBJECTIVES: The objective of this study was to find the event-related brain potential (ERP) waveform features and parameters that maximize the correlation between the ERP components and behavioral performance on a neuropsychological test of language comprehension (PPVT-R) in order to develop an electrophysiological diagnostic technique that can be used in the assessment of aphasic patients. METHODS: ERPs were recorded during a computerized version of the Peabody Picture Vocabulary Test-Revised (PPVT-R, Form M). In the computerized version, a picture is presented followed by a congruent or incongruent spoken word. A derived measure was calculated from the ERP differentiation between congruent and incongruent words. The traditional PPVT-R (Form L) was also administered for comparison purposes. The participants included 10 left-sided stroke patients. RESULTS: The N400 was the primary component elicited to incongruent spoken words. Following optimization procedures, a statistical correlation (Pearson r=0.86) was found between the derived N400 measures and the neuropsychological test scores. Examination of the scatter plot confirmed that the relationship was linear. The derived N400 measure was defined primarily as the mean of the t-scores obtained from the incongruent and congruent waveform comparison, within the temporal interval that encompasses the N400. CONCLUSIONS: This novel quantification technique links ERPs with neuropsychological data at an unprecedented level. Given the high correlation, a regression line could reasonably be used to estimate a patient's language ability using only ERPs. However, before these findings can be accepted fully, these results need to be replicated in larger samples and across other paradigms.

Adult↗
PubMedDate not supplied

Prognostic determination in anoxic-ischemic and traumatic encephalopathies.

Clinical assessment of the unresponsive patient is limited to examination of brainstem reflexes and simple motor responses to stimulation. It is thus difficult, especially if brainstem functions are intact, to give early, accurate prognostic information on comatose patients. Neurochemical tests and imaging have not been validated and have significant limitations. Electrophysiologic investigations provide a window into cerebral function and are tested, clinically useful, safe, available, and inexpensive. Persistent abnormalities of brainstem auditory evoked potentials and short-latency somatosensory evoked potentials reliably indicate the likelihood permanent vegetative state or death. Conversely, the presence of "cognitive" event-related brain potentials (e.g., P300 and mismatch negativity) reflects the functional integrity of higher-level information processing and, therefore, the likelihood of capacity for cognition. A combined clinical and electrophysiologic approach provides optimal prediction of outcome and level of disability.

Brain Injuries↗