Memorization of "unrelated" word strings by young nonpsychotic schizophrenics.

Used multiple word lists with low contextual constraints to examine nonorganizational processes or "strategies" which might be operating in single-trial free recall by schizophrenics. Ss were 20 young nonpsychotic schizophrenics and 20 normal controls. The schizophrenics, as compared to the normals, showed limited storage capacities of the primary and secondary memories, vulnerability to intrusion, slow response time, inefficiency in utilizing stimulus contiguity for organization, and consequential recall deficit. These findings, with those from previous investigations, suggest that both organizational and nonorganizational dysfunctions may underlie the schizophrenics' poor performance. The possibility that nonorganizational processes may be integral parts of mnemonic organization is discussed. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scope of word meaning activation during sentence processing by young and older adults

In a naming experiment, we examined word meaning activation on-line during sentence processing by younger and older adults. Sentences were biased to either the most or least frequently used meaning of a sentence-final ambiguous word. In order to determine the scope of initial meaning activation, targets represented either high- or low-salient semantic relationships to a single sense of the ambiguous word in context. Both age groups evidenced context-dependent activation of word meaning. In addition, context activated a wide scope of meaning that included both high- and low-salience aspects of the ambiguous words. These results contradict predictions based on the inhibition deficit hypothesis (Hasher & Zacks, 1988). However, they are compatible with an interactive activation model of language comprehension that does not discriminate among age groups.     

The activation of phonology during silent Chinese word reading.

The role of phonology in silent Chinese compound-character reading was studied in 2 experiments with native Chinese speakers performing a semantic relatedness judgment task. There was significant interference from a homophone of a "target" word that was semantically related to an initially presented cue word whether the homophone was orthographically similar to the target or not. This interference was only observed for exact homophones (i.e., those that had the same tone, consonant, and vowel). In addition, the effect was not significantly modulated by target or distractor frequency, nor was it restricted to cases of associative priming. Substantial interference was also found from orthographically similar nonhomophones of the targets. Together these data are best accounted for by a model that allows for parallel access of semantics via 2 routes, 1 directly from orthography to semantics and the other from orthography to phonology to semantics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention constraints of semantic activation during visual word recognition.

The reduction of semantic priming following letter search of the prime suggests that semantic activation can be blocked if attention is allocated to the letter level during word processing. Is this true even for the very fast-acting component of semantic activation? To test this, the authors explored semantic priming of lexical decision at stimulus onset asynchronies (SOAs) of either 200 or 1000 ms. Following semantic prime processing, priming occurred at both SOAs. In contrast, no priming occurred at the long SOA following letter-level processing. Of greatest interest, at the short SOA there was priming following the less demanding consonant/vowel task but not following the more attention-demanding letter search task. Hence, semantic activation can occur even when attention is directed to the letter level, provided there are sufficient resources to support this activation. The authors conclude that the default setting during word recognition is for fast-acting activation of the semantic system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Successive activation of both cerebral hemispheres during cued word generation

Most humans have a left hemispheric dominance for language. However, during diagnostic language testing there also is activation of the right hemisphere, which is probably related to attention. To investigate further the role of attention during language production we monitored cerebral blood flow velocities in the middle cerebral arteries by continuous bilateral transcranial Doppler ultrasonography (TCD) in nine right-handed subjects. During cued word generation, a successive activation of the right hemisphere in the preparatory phase, and of the left hemisphere during word searching was demonstrated. These findings indicate that attentional processes precede verbal activation and that the two procedures can be separated by comparative blood flow velocity measurement.     

The activation of word class information during speech production.

In 5 picture-word interference experiments the activation of word class information was investigated. The first experiment, in which subjects used bare nouns to describe the pictures, failed to reveal any interference effect of noun distractor words as opposed to closed-class distractor words. In the next 4 experiments the pictures were named by using a definite determiner and the noun completing a sentence fragment. The data demonstrate that noun distractors interfere more strongly with picture naming than do non-noun distractors. This held for both visual and auditory presentation of the distractor words. The interference effect showed up in a time window where semantic interference can usually be observed, supporting the assumption that at an early stage of lexical access semantic and syntactic activation processes overlap. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activation patterns of covert word generation detected by fMRI: comparison with 3D PET

PURPOSE: The aim of our study was to compare the activation patterns of higher cognitive function detected by functional MRI (fMRI) with those by H2(15)O positron emission tomography (PET). METHOD: Activation studies with both modalities were performed in six normal volunteers with identical covert word generation tasks and statistical analysis. For PET, each subject had five rest scans and five task scans at 10 min intervals. fMRI was performed with a 1.5 T magnet using T2*-weighted echo planar sequences. Each scanning session consisted of two rest and two task periods of 30 s each, alternating rest and task. RESULTS: In group analysis, the activation patterns on both PET and fMRI were similar, whereas the deactivation patterns differed, presumably due to the noise of fMRI. In single-subject analysis, PET showed fewer activated areas and fMRI showed more areas of activation than in group analysis. CONCLUSION: fMRI has an advantage over 3D PET in its better signal-to-noise ratio for detecting change in neuronal activity for higher brain function.     

Psychometrically matched tasks evaluating differential fMRI activation during form and motion processing.

Objective: Deficits in visual perception and working memory are commonly observed in neuropsychiatric disorders and have been investigated using functional MRI (fMRI). However, interpretation of differences in brain activation may be confounded with differences in task performance between groups. Differences in task difficulty across conditions may also pose interpretative issues in studies of visual processing in healthy subjects. Method: To address these concerns, the present study characterized brain activation in tasks that were psychometrically matched for difficulty; fMRI was used to assess brain activation in 10 healthy subjects during discrimination and working memory judgments for static and moving stimuli. For all task conditions, performance accuracy was matched at 70.7%. Results: Areas associated with V2 and V5 in the dorsal stream were activated during motion processing tasks and V4 in the ventral stream were activated during form processing tasks. Frontoparietal areas associated with working memory were also statistically significant during the working memory tasks. Conclusions: Application of psychophysical methods to equate task demands provides a practical method to equate performance levels across conditions in fMRI studies and to compare healthy and cognitively impaired groups at comparable levels of effort. These psychometrically matched tasks can be applied to patients with a variety of cognitive disorders to investigate dysfunction of multiple a priori defined brain regions. Measuring the changes in typical activation patterns in patients with these diseases can be useful for monitoring disease progression, evaluating new drug treatments, and possibly for developing methods for early diagnosis. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Eye movements to pictures reveal transient semantic activation during spoken word recognition.

[Correction Notice: An erratum for this article was reported in Vol 32(2) of Journal of Experimental Psychology: Learning, Memory, and Cognition (see record 2007-16796-001). The note to Appendix B (Stimuli Used in Experiment 2) on p. 14 contained errors. The fourth sentence, "For example, for participants receiving List A, lock was the target, key was the semantically related object, deer was the target's control, and apple was the related objects control" should read as follows: "For example, for participants receiving List A, logs was the target, key was the semantic onset competitor, and apple was the competitor's control."] Two experiments explore the activation of semantic information during spoken word recognition. Experiment 1 shows that as the name of an object unfolds (e.g., lock), eye movements are drawn to pictorial representations of both the named object and semantically related objects (e.g., key). Experiment 2 shows that objects semantically related to an uttered word's onset competitors become active enough to draw visual attention (e.g., if the uttered word is logs, participants fixate on key because of partial activation of lock), despite that the onset competitor itself is not present in the visual display. Together, these experiments provide detailed information about the activation of semantic information associated with a spoken word and its phonological competitors and demonstrate that transient semantic activation is sufficient to impact visual attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Theoretical situation of brain white matter tracts evaluated by three-dimensional MRI

BACKGROUND: Screening for psychological distress in cancer patients is important, considering the high prevalence of psychiatric disorders responsive to treatment. The aim of this study is to test the psychometric properties of the Psychological Distress Inventory (PDI), a 13-item self-administered questionnaire developed to measure psychological distress in cancer patients. PATIENTS AND METHODS: The PDI was tested in three samples of 434 cancer patients. In the first sample (n = 102) it was administered with the State Trait Anxiety Inventory (STAI) and with the Eysenck Personality Questionnaire (EPQ). Its validity as a screening method for psychiatric disorders was evaluated through a clinical interview in the second sample (n = 107). The third sample (n = 225) provided information on the ability of the PDI to discriminate among patients in different clinical phases of disease and allowed an estimate of the prevalence of psychiatric disorders in these groups of patients. RESULTS: A 0.88 alpha coefficient was obtained in the whole study sample. The correlations with the STAI scales were > 0.70. A positive correlation with neuroticism (r = 0.59) and a negative correlation with extroversion (r = -0.34) was observed. In the second sample, 67 patients (62.6%) received a psychiatric diagnosis according to the ICD-X criteria. The mean PDI scores were significantly lower for the 40 patients with no psychiatric diagnosis (mean 24.5) as compared with the 49 patients with adjustment disorders (mean 36.4) and with the 12 patients with depressive disorders (mean 40.8). The area under curve, estimated through a Receiver-Operating Characteristics analysis, was 0.88. A cut-off of 29 was associated with a 75% sensitivity and a 85% specificity. In the third sample, the lowest PDI scores were in patients with no evidence of disease (mean 24.7, 95% CL 23.0-26.4) as compared to patients undergoing antineoplastic treatment (mean 30.9, 95% CL 28.9-32.9) and to patients under palliative therapy (mean 36.0, 95% CL 34.0-37.9). The estimated prevalence of patients with psychiatric disorders in these three groups were respectively 5.0, 56.6 and 98.8%. CONCLUSIONS: Our results suggest that the PDI is a reliable and valid tool for measuring psychological distress in cancer patients and to detect psychiatric disorders through a screening procedure.     

In situ activation pattern of Drosophila EGF receptor pathway during development

Signaling cascades triggered by receptor tyrosine kinases (RTKs) participate in diverse developmental processes. The active state of these signaling pathways was monitored by examination of the in situ distribution of the active, dual phosphorylated form of mitogen-activated protein kinase (ERK) with a specific monoclonal antibody. Detection of the active state of the Drosophila epidermal growth factor receptor (DER) pathway allowed the visualization of gradients and boundaries of receptor activation, assessment of the distribution of activating ligands, and analysis of interplay with the inhibitory ligand Argos. This in situ approach can be used to monitor other receptor-triggered pathways in a wide range of organisms.     

Dynamic contrast perception assessed by pattern masking

The perceived contrast of a pulsed grating varies markedly with the exposure duration and spatial frequency of the grating. We studied dynamic changes in perceived grating contrast with a pattern-masking paradigm. We measured masking of a brief, localized test pattern (a D6 stimulus, 30 ms in duration) by fixed-contrast cosine grating patterns of varying duration (50-500 ms). The cosine mask pattern had spatial frequency of either 1 or 6 cycles per degree (cpd) at a contrast of 0.3. The D6 test pattern was centered on a light bar of the mask and was either positive peak contrast (same-polarity test and mask) or negative peak contrast (opposite-polarity test and mask). In Experiment 1, the test and mask had simultaneous onset. With a 6-cpd mask, the same-polarity test-threshold elevation versus mask-duration function increases monotonically. For a 1-cpd mask, the same-polarity threshold-mask-duration function is nonmonotonic, with peak masking effect produced by a grating pulse of 80-100 ms. These masking effects are closely congruent with known dynamic contrast effects. With negative tests, masking-duration functions are elevated from same-polarity functions and are essentially similar in shape for 1- and 6-cpd masks. The elevated thresholds suggest inhibitory interaction between ON and OFF pathways, with a similar time course across spatial frequency. In Experiment 2, the D6 test was delayed from mask onset by 33 ms. Positive contrasts only were employed. For 1-cpd stimuli, the delay of test greatly reduced masking at all mask durations and eliminated the nonmonotonic function. This suggests that for low-spatial-frequency patterns, perceived contrast is determined by an early peak component of the neural response. But for 6-cpd stimuli, masking of the delayed test was somewhat greater at all mask durations, consistent with a gradually increasing underlying neural response to the grating. Finally, in Experiment 3, same-polarity masking effects at both spatial frequencies were replicated with negative-contrast test and mask (OFF pathway mediation). This indicates that the ON and OFF pathways have similar response dynamics.     

Sequential hemodynamic activation of motor areas and the draining veins during finger movements revealed by cross-correlation between signals from fMRI

Activity in the human supplementary motor area (SMA), primary motor cortex (M1), and the draining vein of the motor cortex during a visually triggered finger opposition task was measured by functional magnetic resonance imaging with a repetition time of 1 s. Sequential hemodynamic activation in these areas was revealed by cross-correlating a signal sequence in M1 directly with signal sequences from SMA and the draining vein, and applying polynomial fitting with the aid of Akaike's information criterion. We succeeded in detecting a time delay of approximately 0.5 s between the activations of SMA and M1, and a delay of nearly 1.3 s between the activations of M1 and its draining vein. The new combination of fMRI and data analysis techniques has attained a time resolution comparable to those in preceding studies that used shorter fMRI repetition times of 100-200 ms.     

Temporal dynamics of brain activation during a working memory task

Working memory is responsible for the short-term storage and online manipulation of information necessary for higher cognitive functions, such as language, planning and problem-solving. Traditionally, working memory has been divided into two types of processes: executive control (governing the encoding manipulation and retrieval of information in working memory) and active maintenance (keeping information available 'online'). It has also been proposed that these two types of processes may be subserved by distinct cortical structures, with the prefrontal cortex housing the executive control processes, and more posterior regions housing the content-specific buffers (for example verbal versus visuospatial) responsible for active maintenance. However, studies in non-human primates suggest that dorsolateral regions of the prefrontal cortex may also be involved in active maintenance. We have used functional magnetic resonance imaging to examine brain activation in human subjects during performance of a working memory task. We used the temporal resolution of this technique to examine the dynamics of regional activation, and to show that prefrontal cortex along with parietal cortex appears to play a role in active maintenance.     

Sex differences in prefrontal cortical brain activity during fMRI of auditory verbal working memory.

Functional imaging studies of sex effects in working memory (WMEM) are few, despite significant normal sex differences in brain regions implicated in WMEM. This functional MRI (fMRI) study tested for sex effects in an auditory verbal WMEM task in prefrontal, parietal, cingulate, and insula regions. Fourteen healthy, right-handed community subjects were comparable between the sexes, including on WMEM performance. Per statistical parametric mapping, women exhibited greater signal intensity changes in middle, inferior, and orbital prefrontal cortices than men (corrected for multiple comparisons). A test of mixed-sex groups, comparable on performance, showed no significant differences in the hypothesized regions, providing evidence for discriminant validity for significant sex differences. The findings suggest that combining men and women in fMRI studies of cognition may obscure or bias results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right-sided human prefrontal brain activation during acquisition of conditioned fear.

This H/21?O positron emission tomography (PET) study reports on relative regional cerebral blood flow (rCBF) alterations during fear conditioning in humans. In the PET scanner, subjects viewed a TV screen with either visual white noise or snake videotapes displayed alone, then with electric shocks, followed by final presentations of white noise and snakes. Autonomic nervous system responses confirmed fear conditioning only to snakes. To reveal neural activation during acquisition, while equating sensory stimulation, scans during snakes with shocks and white noise alone were contrasted against white noise with shocks and snakes alone. During acquisition, rCBF increased in the right medial frontal gyrus, supporting a role for the prefrontal cortex in fear conditioning to unmasked evolutionary fearrelevant stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebral networks and functional brain asymmetry: evidence from regional metabolic changes during word repetition

Word repetition causes a significant bilateral metabolic increase in both superior temporal cortices. Frontal speech areas are less activated despite their presumable speech competence. We investigated in this study the relationship between frontal and temporal cortical areas during word repetition. We measured regional cerebral metabolic rates of glucose (CMRGI) in 15 normal subjects with positron emission tomography (PET) at rest and during word repetition. Significant correlations connected frontal and temporal areas of both hemispheres, notwithstanding their different levels of mean metabolic activation. The left planum temporale was a hub of significant interregional correlations, in contrast to its contralateral mate. This study indicates that an asymmetric network of significant connections orchestrates the speech-relevant cortical areas according to the actual needs of speech processing.     

Dissociation of saccade-related and pursuit-related activation in human frontal eye fields as revealed by fMRI

The location of the human frontal eye fields (FEFs) underlying horizontal visually guided saccadic and pursuit eye movements was investigated with the use of functional magnetic resonance imaging in five healthy humans. Execution of both saccadic and pursuit eye movements induced bilateral FEF activation located medially at the junction of the precentral sulcus and the superior frontal sulcus and extending laterally to the precentral gyrus. These findings extend previous functional imaging studies by providing the first functional imaging evidence of a specific activation in the FEF during smooth pursuit eye movements in healthy humans. FEF activation during smooth pursuit performance was smaller than during saccades. This finding, which may reflect the presence of a smaller pursuit-related region area in human FEF than the saccade-related region, is consistent with their relative size observed in the monkey. The mean location of the pursuit-related FEF was more inferior and lateral than the location of the saccade-related FEF. These results provide the first evidence that there are different subregions in the human FEF that are involved in the execution of two different types of eye movements, namely saccadic and pursuit eye movements. Moreover, this study provides additional evidence that the human FEF is located in Brodmann's area 6, unlike the monkey FEF which is located in the posterior part of Brodmann's area 8.     

Visual word recognition during reading is followed by subvocal articulation.

Three experiments examined whether the identification of a visual word is followed by its subvocal articulation during reading. An irrelevant spoken word (ISW) that was identical, phonologically similar, or dissimilar to a visual target word was presented when the eyes moved to the target in the course of sentence reading. Sentence reading was further accompanied by either a sequential finger tapping task (Experiment 1) or an articulatory suppression task (Experiment 2). Experiment 1 revealed sound-specific interference from a phonologically similar ISW during posttarget viewing. This interference was absent in Experiment 2, where similar and dissimilar ISWs impeded target and posttarget reading equally. Experiment 3 showed that articulatory suppression left the lexical processing of visual words intact and that it did not diminish the influence of visual word recognition on eye guidance. The presence of sound-specific interference during posttarget reading in Experiment 1 is attributed to deleterious effects of a phonologically similar ISW on the subvocal articulation of a target. Its absence in Experiment 2 is attributed to the suppression of a target’s subvocal articulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)