Common basal extrastriate areas for the semantic processing of words and pictures.

OBJECTIVE: The recognition potential (RP) is an electrophysiological brain response which is sensitive to the semantic processing of meaningful stimuli. In this study we attempt to elucidate the topography and neural origin of the RP evoked by pictures and to compare it with the RP evoked by words. METHODS: Words, pictures, Chinese characters and control stimuli were presented to 20 subjects following the rapid stream stimulation procedure. The activity was recorded using 60 cephalic electrodes. RESULTS: We found a RP displaying its maximal amplitude at the left inferior parieto-occipital electrode (PO7) for words and at the right homologue electrode (PO8) for pictures and Chinese characters. Both the amplitude and the latency of the RP were larger in the case of words. A profile analysis indicated that the neural generators of the RP were common regardless of the type of stimulus, and a dipole analysis placed them about the lingual gyrus. CONCLUSIONS: Words and pictures share the same neural generators for the RP despite of subtle differences in lateralization. This is interpreted as an index of a multimodal semantic processing in basal extrastriate areas.     

Negative content enhances stimulus‐specific cerebral activity during free viewing of pictures,faces, and words

Negative visual stimuli have been found to elicit stronger brain activation than do neutral stimuli. Such emotion effects have been shown for pictures, faces, and words alike, but the literature suggests stimulus‐specific differences regarding locus and lateralization of the activity. In the current functional magnetic resonance imaging study, we directly compared brain responses to passively viewed negative and neutral pictures of complex scenes, faces, and words (nouns) in 43 healthy participants (21 males) varying in age and demographic background. Both negative pictures and faces activated the extrastriate visual cortices of both hemispheres more strongly than neutral ones, but effects were larger and extended more dorsally for pictures, whereas negative faces additionally activated the superior temporal sulci. Negative words differentially activated typical higher‐level language processing areas such as the left inferior frontal and angular gyrus. There were small emotion effects in the amygdala for faces and words, which were both lateralized to the left hemisphere. Although pictures elicited overall the strongest amygdala activity, amygdala response to negative pictures was not significantly stronger than to neutral ones. Across stimulus types, emotion effects converged in the left anterior insula. No gender effects were apparent, but age had a small, stimulus‐specific impact on emotion processing. Our study specifies similarities and differences in effects of negative emotional content on the processing of different types of stimuli, indicating that brain response to negative stimuli is specifically enhanced in areas involved in processing of the respective stimulus type in general and converges across stimuli in the left anterior insula.     

Semantic priming by pictures and words in the cerebral hemispheres

In order to determine whether pictures would act as more effective semantic primes than words in the right cerebral hemisphere, automatic semantic activation in intact hemispheres was studied with primed GO-NOGO lexical decision tasks by presenting word-word and picture-word pairs to the left visual field (right hemisphere) or to the right visual field (left hemisphere). Response times in Experiment 1 showed that categorically related targets (e.g., TABLE-BED) were primed only in the right visual field after both word and picture primes. Experiment 2 found that picture primes activated the representations of the corresponding written names in both visual fields. These observations suggest that the range of automatic semantic activation is larger in the left than in the right hemisphere. The results implicate that semantic categories may be organized in a different fashion in the left than the right hemisphere.     

Brain activation of reading korean words and recognizing pictures by Korean native speakers: a functional magnetic resonance imaging study

Even though the Korean words are characterized as phonemes like other alphabetic languages, their shape resembles much more morphemes like Chinese characters. The main purpose of the study is to explore neural mechanisms of reading Korean words and recognizing pictures by Korean native speakers using functional magnetic resonance imaging technique. In the experimental results, the authors could see commonly activated areas in occipito-temporal region bilaterally, whereas frontal and temporal region was activated only while reading Korean words. Left middle frontal activation of Korean words was regarded to be involved in the phonological and semantic processing. Right anterior cingulate (BA 32) activation seems to be related with language and sound organization and superior temporal (BA 29) activation might be involved in the processing of phonological system to which tonal information is attached. Right medial frontal (BA 8) activation was reported in the results. The authors suggest the activation of this area is related with nonverbal visual higher order control or visuospatial analysis of Korean words in their experimental tasks.     

Brain activation of reading Korean words and recognizing pictures by Korean native speakers: A functional magnetic resonance imaging study

Even though the Korean words are characterized as phonemes like other alphabetic languages, their shape resembles much more morphemes like Chinese characters. The main purpose of the study is to explore neural mechanisms of reading Korean words and recognizing pictures by Korean native speakers using functional magnetic resonance imaging technique. In the experimental results, the authors could see commonly activated areas in occipito-temporal region bilaterally, whereas frontal and temporal region was activated only while reading Korean words. Left middle frontal activation of Korean words was regarded to be involved in the phonological and semantic processing. Right anterior cingulate (BA 32) activation seems to be related with language and sound organization and superior temporal (BA 29) activation might be involved in the processing of phonological system to which tonal information is attached. Right medial frontal (BA 8) activation was reported in the results. The authors suggest the activation of this area is related with nonverbal visual higher order control or visuospatial analysis of Korean words in their experimental tasks.     

Short-term memory for pictures and words by mentally retarded and nonretarded persons

Mentally retarded and nonretarded persons were compared in a Brown-Peterson short-term memory task for the retention of words and pictures over intervals up to 30 seconds. The retarded subjects forgot more rapidly over the initial 10 seconds. They also retained pictures better than they did words; the nonretarded subjects retained these stimuli equally well. The results were theoretically interpreted as reflecting a structural memory deficit in retarded individuals, who were viewed as having greater facility with an imaginal memory code than with a verbal code. Transforming information from one code to another may also have been more difficult for retarded persons.     

Differences in word associations to pictures and words

Normal subjects were asked to produce the "first word that comes to mind" in response to pictures or words that differed with respect to manipulability and animacy. In separate analyses across subjects and items, normal subjects produced a significantly higher proportion of action words (that is, verbs) to pictures as compared to words, to manipulable as compared to non-manipulable stimuli and to inanimate as compared to animate stimuli. The largest proportion of action words was elicited by pictures of non-living, manipulable objects. Furthermore, associates to words matched standard word associates significantly more often than those elicited by pictures. These data suggest that pictures and words initially contact different forms of conceptual information and are consistent with an account of semantic organization that assumes that information is distributed across different domains reflecting the mode of acquisition of that knowledge.     

Auditory activation of cortical visual areas in cats after early visual deprivation

Auditory activation of the primary visual cortex (area 17) and two extrastriate visual cortical areas - the anterolateral lateral suprasylvian area (ALLS) and anteromedial lateral suprasylvian area (AMLS), was investigated in visually impaired cats. Impairment was accomplished shortly after birth by bilateral eyelid suturing (binocularly deprived cats, BD) or bilateral enucleation (binocularly enucleated cats, BE). In BE cats, the optic nerve and chiasm were entirely degenerated. No cortical atrophy or cytoarchitectural malformation was noticed in either BD or BE cats. In both normal and impaired cats we found auditory-responsive cells in the ALLS and AMLS, areas that are considered strictly visual. The most remarkable finding was an increase in the relative number of these auditory cells in the BD and BE cats, which was more prominent in the latter. Some auditory-responsive cells were also found in area 17 of BE cats. On the basis of formal calculation, it is tempting to suggest that the increase in relative number of auditory cells in these areas reflects the transformation of all the visual cells in the ALLS of BD and BE cats into auditory cells. In BE cats, all bimodal cells and an appreciable percentage of non-responsive cells also had transformed to auditory cells. In the AMLS of BD cats, it is primarily the bimodal cells that become auditory cells, whereas in BE cats all the visual and bimodal cells as well as non-responsive cells undergo this transformation. This assumption, however, is one possible interpretation of our results but not the only one. Other modes of neuronal plasticity that might yield similar results in the visually deprived cats can not be ruled out.     

Differential amygdala activation to negative and positive emotional pictures during an indirect task

The role of the amygdala for the processing of valence and arousal is a matter of debate. Using event-related functional magnetic resonance imaging, we tested valence-specific amygdala effects during attentional distraction. Subjects attended to a matching task in the foreground of neutral pictures, and of negative and positive pictures matched for arousal. Negative pictures elicited stronger amygdala activation than neutral or positive pictures, suggesting valence-specific amygdala responses under attentional load.     

When written words become moving pictures: complex visual hallucinations on stimulation of the lateral occipital lobe

Electrical stimulation of the human epileptic brain is used mainly for identification of eloquent cortical regions such as motor and speech areas. Other stimulation responses include the patient's epileptic auras and seizures. In addition, experiential phenomena may be elicited. Here we describe the reproducible initiation of a structured complex visual hallucination on stimulation of the left lateral occipital cortex (superior part of Brodmann area 19, close to the angular gyrus of the parietal lobe). Our findings illustrate that stimulation of the left temporo-parieto-occipital junction may activate networks of visual perception (color, pattern, movement, rotation, shape, and memory) independent of the cortical hierarchy from elementary to complex information.     

Increased medial temporal lobe activation during the passive viewing of emotional and neutral facial expressions in schizophrenia

INTRODUCTION: Patients with schizophrenia show deficits in facial affect and facial identity recognition and exhibit structural and neurophysiological abnormalities in brain regions known to mediate these processes. Functional neuroimaging studies of neural responses to emotional facial expressions in schizophrenia have reported both increases and decreases in medial temporal lobe (MTL) activity in schizophrenia. Some of this variability may be related to the tasks performed and the baseline conditions used. Here we tested whether MTL responses to human faces in schizophrenia are abnormal when unconstrained by a cognitive task and measured relative to a low-level baseline (fixation) condition. METHODS: 15 patients with schizophrenia and 16 healthy control subjects underwent functional magnetic resonance imaging (fMRI) while passively viewing human faces displaying fearful, happy, and neutral emotional expressions. RESULTS: Relative to control subjects, the patients demonstrated (1) significantly greater activation of the left hippocampus while viewing all three facial expressions and (2) increased right amygdala activation during the initial presentation of fearful and neutral facial expressions. CONCLUSIONS: In schizophrenia, hippocampal and amygdala activity is elevated during the passive viewing of human faces.     

White matter maturation in visual and motor areas predicts the latency of visual activation in children

In humans, white matter maturation is important for the improvement of cognitive function and performance with age. Across studies the variables of white matter maturity and age are highly correlated; however, the unique contributions of white matter to information processing speed remain relatively unknown. We investigated the relations between the speed of the visually-evoked P100m response and the biophysical properties of white matter in 11 healthy children performing a simple, visually-cued finger movement. We found that: (1) the latency of the early, visually-evoked response was related to the integrity of white matter in both visual and motor association areas and (2) white matter maturation in these areas accounted for the variations in visual processing speed, independent of age. Our study is a novel investigation of spatial-temporal dynamics in the developing brain and provides evidence that white matter maturation accounts for age-related decreases in the speed of visual response. Developmental models of cortical specialization should incorporate the unique role of white matter maturation in mediating changes in performance during tasks involving visual processing.     

Brain activation by disgust-inducing pictures in obsessive-compulsive disorder.

BACKGROUND: There is growing interest in the role of disgust in the pathogenesis of obsessive-compulsive disorder (OCD). METHODS: Eight OCD subjects with contamination preoccupations and eight gender- and age-matched healthy volunteers viewed pictures from the International Affective Picture System during functional magnetic resonance imaging scans. RESULTS: A different distribution of brain activations was found during disgust-inducing visual stimulation in several areas, most notably the insula, compared with neutral stimulation in both OCD subjects and healthy volunteers. Furthermore, whereas activation during the threat-inducing task in OCD subjects showed a pattern similar to that in healthy volunteers, the pattern of activation during the disgust-inducing task was significantly different, including greater increases in the right insula, parahippocampal region, and inferior frontal sites. CONCLUSIONS: This pilot study supports the relevance of disgust in the neurocircuitry of OCD with contamination-preoccupation symptoms; future studies looking at non-OCD individuals with high disgust ratings, non-contamination-preoccupied OCD individuals, and individuals with other anxiety disorders are needed.     

Differential and co-involvement of areas of the temporal and parietal streams in visual tasks

Transcranial magnetic stimulation (TMS) is particularly useful in teasing apart the contrasting contributions of different anatomical and functional systems in particular aspects of behaviour, for example the involvement of the dorsal and ventral visual streams in tasks involving the perception of distance, shape and colour. In order to investigate the dual involvement of two areas, namely right posterior parietal cortex (PPC) and lateral occipital cortex (LO), in a distance discrimination task, neural processing in both areas was concurrently disrupted using dual site TMS. Although there was no change in error rates, reaction time was significantly lengthened over that seen with TMS over either site alone. This additive effect indicates that both PPC and LO are concurrently active and essential for efficient processing of this task. The second experiment investigated the specificity of function within the ventral stream. Performance was assessed for distance and shape discrimination when TMS was applied to our original LO site and an area rostral to V5 but still part of the lateral occipital complex (rostral LOC) that is activated in form and colour discrimination. Performance deficits were restricted to TMS over LO; no significant impairment for either task followed TMS at the rostral LOC site.     

False recognition of incidentally learned pictures and words in primary progressive aphasia

Recognition memory was tested in patients with primary progressive aphasia (PPA), a language based dementia with relative preservation of memory for at least the first 2 years. The goal of the study was two-fold: (1) to compare true and false recognition rates for words versus pictures in patients with PPA and cognitively intact controls and (2) to determine if the semantic relatedness of distracters-to-targets influences recognition memory performance. Overall, performance of PPA patients was worse for words than pictures. PPA patients and healthy elderly controls showed similar recognition rates for studied items. However, the patients had significantly more false alarms than controls, particularly to semantically related items. This suggests that the aphasia in PPA patients contributes to their difficulty in selecting among items within a semantic class.     

Differential brain activation in anorexia nervosa to Fat and Thin words during a Stroop task

We measured brain activation in six anorexia nervosa patients and six healthy controls performing a novel emotional Stroop task using Fat, Thin, and Neutral words, and words made of XXXXs. Reaction times increased in the patient group in Thin and Fat conditions. In the Thin-XXXX contrast, patients showed greater activation than controls at the junction of left insula, frontal and temporal lobes and in left middle and medial frontal gyri. In the Fat-XXXX contrast, controls showed greater activation in left dorsolateral prefrontal cortex and right parietal areas. Mechanisms underlying attentional bias in anorexia nervosa likely differ under conditions of positive and negative valence. This paradigm is a promising tool to examine neural mediation of emotional response in anorexia nervosa.     

Common effects of emotional valence, arousal and attention on neural activation during visual processing of pictures.

Emotion and attention heighten sensitivity to visual cues. How neural activation patterns associated with emotion change as a function of the availability of attentional resources is unknown. We used positron emission tomography (PET) and 15O-water to measure brain activity in male volunteers while they viewed emotional picture sets that could be classified according to valence or arousal. Subjects simultaneously performed a distraction task that manipulated the availability of attentional resources. Twelve scan conditions were generated in a 3 x 2 x 2 factorial design involving three levels of valence (pleasant, unpleasant and neutral), two levels of arousal and two levels of attention (low and high distraction). Extrastriate visual cortical and anterior temporal areas were independently activated by emotional valence, arousal and attention. Common areas of activation derived from a conjunction analysis of these separate activations revealed extensive areas of activation in extrastriate visual cortex with a focus in right BA18 (12, -88, -2) (Z=5.73, P < 0.001 corrected) and right anterior temporal cortex BA38 (42, 14, -30) (Z=4.03, P < 0.05 corrected). These findings support an hypothesis that emotion and attention modulate both early and late stages of visual processing.     

Shift of visual field advantage by learning experience of foreign words

Effects of Hebrew words learning on visual field advantage were examined with Japanese subjects. Subjects who showed no visual field advantage to Hebrew words in the first testing were assigned randomly into four experimental groups; learn pronunciation only, learn meaning only, learn both pronunciation and meaning, and learn nothing. After then, subjects were re-tested for Hebrew words discrimination. A right visual field advantage appeared in both pronunciation only and pronunciation plus meaning groups. These results suggest that mastery of pronunciation seems to be a crucial factor in producing a shift of visual field advantage.     

Covert processing of words and pictures in nonsemantic variants of primary progressive aphasia

The inability to name objects (anomia) is one of the most common findings in the neurologic examination of primary progressive aphasia (PPA). In the semantic variant of PPA, the anomia is profound and reflects a combination of object naming and word comprehension deficits. In contrast, nonsemantic variants of PPA display a more selective impairment of object naming, without corresponding impairments of word comprehension. The aim of the present study was to explore the nature of the anomia in nonsemantic variants of PPA with a sensitive chronometric test of covert word/picture association. We tested priming effects in 12 patients with nonsemantic variant of PPA and 18 controls. Stimuli consisted of written words and line pictures of concrete objects. Within-format (word-word and picture-picture) and cross-format (word-picture and picture-word) priming effects were assessed by measuring the shortening of response times to the second versus initial presentation of corresponding stimulus pairs. In addition to the expected impairment of picture-to-word priming, a condition simulating object naming, the nonsemantic PPA patients also showed unexpected impairments of word-to-picture and word-to-word priming. Picture-to-picture priming was preserved, demonstrating the selectivity of the deficit for lexical processing. These findings show that the information processing bottleneck in patients with nonsemantic variants of PPA is not confined to the stage of lexical access but that it also extends into the prior levels of lexical semantics. The boundaries between the semantic and nonsemantic variants are therefore far from rigid.     

Event-related potentials for category-specific information during passive viewing of faces and objects

Normal subjects passively viewed an upright or inverted face or objects during recording of event-related potentials. Face inversion augmented N170 amplitude and latency in the temporal region, but only the latency in the parietal region. The same manipulation slowed down the onset of the P220 and caused disappearance of the N300, whereas none of these effects was seen after object inversion. Item-specific processing of objects was observed, namely disappearance of the N190 and the appearance of a P170 wave in the left posterior hemisphere to one object but not the other. These results are concordant with the hypothesis of category-specific processing during the recognition of faces and objects.