Person:

Caramazza, Alfonso

One important finding with the picture–word interference paradigm is that picture-naming performance is facilitated by the presentation of a distractor (e.g., CAP) formally related to the picture name (e.g., “cat”). In two picture-naming experiments we investigated the nature of such form facilitation effect with Mandarin Chinese, separating the effects of phonology and orthography. Significant facilitation effects were observed both when distractors were only orthographically or only phonologically related to the targets. The orthographic effect was overall stronger than the phonological effect. These findings suggest that the classic form facilitation effect in picture–word interference is a mixed effect with multiple loci: it cannot be attributed merely to the nonlexical activation of the target phonological segments from the visual input of the distractor. It seems instead that orthographically only related distractors facilitate the lexical selection process of picture naming, and phonologically only related distractors facilitate the retrieval of target phonological segments.

Congenital deafness causes large changes in the auditory cortex structure and function, such that without early childhood cochlear-implant, profoundly deaf children do not develop intact, high-level, auditory functions. But how is auditory cortex organization affected by congenital, prelingual, and long standing deafness? Does the large-scale topographical organization of the auditory cortex develop in people deaf from birth? And is it retained despite cross-modal plasticity? We identified, using fMRI, topographic tonotopy-based functional connectivity (FC) structure in humans in the core auditory cortex, its extending tonotopic gradients in the belt and even beyond that. These regions show similar FC structure in the congenitally deaf throughout the auditory cortex, including in the language areas. The topographic FC pattern can be identified reliably in the vast majority of the deaf, at the single subject level, despite the absence of hearing-aid use and poor oral language skills. These findings suggest that large-scale tonotopic-based FC does not require sensory experience to develop, and is retained despite life-long auditory deprivation and cross-modal plasticity. Furthermore, as the topographic FC is retained to varying degrees among the deaf subjects, it may serve to predict the potential for auditory rehabilitation using cochlear implants in individual subjects.

Previous studies have provided evidence for a tool-selective region in left lateral occipitotemporal cortex (LOTC). This region responds selectively to pictures of tools and to characteristic visual tool motion. The present human fMRI study tested whether visual experience is required for the development of tool-selective responses in left LOTC. Words referring to tools, animals, and nonmanipulable objects were presented auditorily to 14 congenitally blind and 16 sighted participants. Sighted participants additionally viewed pictures of these objects. In whole-brain group analyses, sighted participants showed tool-selective activity in left LOTC in both visual and auditory tasks. Importantly, virtually identical tool-selective LOTC activity was found in the congenitally blind group performing the auditory task. Furthermore, both groups showed equally strong tool-selective activity for auditory stimuli in a tool-selective LOTC region defined by the picture-viewing task in the sighted group. Detailed analyses in individual participants showed significant tool-selective LOTC activity in 13 of 14 blind participants and 14 of 16 sighted participants. The strength and anatomical location of this activity were indistinguishable across groups. Finally, both blind and sighted groups showed significant resting state functional connectivity between left LOTC and a bilateral frontoparietal network. Together, these results indicate that tool-selective activity in left LOTC develops without ever having seen a tool or its motion. This finding puts constraints on the possible role that this region could have in tool processing and, more generally, provides new insights into the principles shaping the functional organization of OTC.

Widely distributed brain regions in temporal, parietal and frontal cortex have been found to be involved in semantic processing, but the anatomical connections supporting the semantic system are not well understood. In a group of 76 right-handed brain-damaged patients, we tested the relationship between the integrity of major white matter tracts and the presence of semantic deficits. The integrity of white matter tracts was measured by percentage of lesion voxels obtained in structural imaging and mean fractional anisotropy values obtained in diffusion tensor imaging. Semantic deficits were assessed by jointly considering the performance on three semantic tasks that vary in the modalities of input (visual and auditory stimuli) and output (oral naming and associative judgement). We found that the lesion volume and fractional anisotropy value of the left inferior fronto-occipital fasciculus, left anterior thalamic radiation, and left uncinate fasciculus significantly correlated with severity of impairment in all three semantic tasks. These associations remained significant even when we controlled for a wide range of potential confounding variables, including overall cognitive state, whole lesion volume, or type of brain damage. The effects of these three white matter tracts could not be explained by potential involvement of relevant grey matter, and were (relatively) specific to object semantic processing, as no correlation with performance on non-object semantic control tasks (oral repetition and number processing tasks) was observed. These results underscore the causal role of left inferior fronto-occipital fasciculus, left anterior thalamic radiation, and left uncinate fasciculus in semantic processing, providing direct evidence for (part of) the anatomical skeleton of the semantic network.

The principles that determine the organization of object representations in ventral temporal cortex (VTC) remain elusive. Here, we focus on the parahippocampal place area (PPA), a region in medial VTC that has been shown to respond selectively to pictures of scenes. Recent studies further observed that this region also shows a preference for large nonmanipulable objects relative to other objects, which might reflect the suitability of large objects for navigation. The mechanisms underlying this selectivity remain poorly understood. We examined the extent to which PPA selectivity requires visual experience. Fourteen congenitally blind and matched sighted participants were tested on an auditory size judgment experiment involving large nonmanipulable objects, small objects (tools), and animals. Sighted participants additionally participated in a picture-viewing experiment. Replicating previous work, we found that the PPA responded selectively to large nonmanipulable objects, relative to tools and animals, in the sighted group viewing pictures. Importantly, this selectivity was also observed in the auditory experiment in both sighted and congenitally blind groups. In both groups, selectivity for large nonmanipulable objects was additionally observed in the retrosplenial complex (RSC) and the transverse occipital sulcus (TOS), regions previously implicated in scene perception and navigation. Finally, in both groups the PPA showed resting-state functional connectivity with TOS and RSC. These results provide new evidence that large object selectivity in PPA, and the intrinsic connectivity between PPA and other navigation-relevant regions, do not require visual experience. More generally, they show that the organization of object representations in VTC can develop, at least partly, without visual experience.

In congenitally blind individuals, many regions of the brain that are typically heavily involved in visual processing are recruited for a variety of nonvisual sensory and cognitive tasks (Rauschecker 1995; Pascual-Leone et al. 2005). This phenomenon—cross-modal plasticity—has been widely documented, but the principles that determine where and how cross-modal changes occur remain poorly understood (Bavelier and Neville 2002). Here, we evaluate the hypothesis that cross-modal plasticity respects the type of computations performed by a region, even as it changes the modality of the inputs over which they are carried out (Pascual-Leone and Hamilton 2001). We compared the fMRI signal in sighted and congenitally blind participants during proprioceptively guided reaching. We show that parietooccipital reach-related regions retain their functional role—encoding of the spatial position of the reach target-even as the dominant modality in this region changes from visual to nonvisual inputs. This suggests that the computational role of a region, independently of the processing modality, codetermines its potential cross-modal recruitment. Our findings demonstrate that preservation of functional properties can serve as a guiding principle for cross-modal plasticity even in visuomotor cortical regions, i.e. beyond the early visual cortex and other traditional visual areas.

Knowledge of the physical attributes of objects is commonly assumed to be distributed near their respective modality-specific brain regions. The exact neural correlates for such knowledge, especially how it is maintained in the resting state, are largely unknown. In the current study, we explored the intrinsic neural basis related to a specific type of object knowledge — color — by investigating the relationship between spontaneous brain activity and color knowledge behavioral performance. We correlated the regional amplitude of spontaneous low-frequency fluctuations (ALFF, a resting-state fMRI parameter) with healthy participants' performance on two object color knowledge tasks (object color verification and color attribute judgment). We found that ALFF in bilateral lingual and fusiform gyri and right inferior occipital gyrus reliably predicted participants' color knowledge performance (correlation coefficients = 0.55–0.70), and that calcarine cortex showed a similar trend, although less stable. Furthermore, the ALFF-behavior correlations for other types of object knowledge (i.e. form, motion and sound) in these regions were minimal and significantly lower than those for color knowledge, suggesting that the effects in the observed regions were not merely due to general object processing. Furthermore, we showed that functional connectivity strengths of the lingual/fusiform and inferior occipital regions are significantly associated with color knowledge performance, indicating that they work as a network to support color knowledge processing or the acquisition of such knowledge. Our findings show the critical role of ventral medial occipito-temporal regions in processing or acquiring color knowledge and highlight the behavioral significance of spontaneous brain activity in the resting state.

In human lateral temporal cortex, some regions show specific sensitivity to human motion. Here we examine whether such effects reflect a general biological-nonbiological organizational principle or a process specific to human-agent processing by comparing processing of human, animal, and tool motion in a functional magnetic resonance imaging (fMRI) experiment with healthy participants and a voxel-based lesion-symptom mapping (VLSM) study of patients with brain damage (77 stroke patients). The fMRI experiment revealed that in the lateral temporal cortex, the posterior superior temporal sulcus shows a preference for human and animal motion, whereas the middle part of the right superior temporal sulcus/gyrus (mSTS/STG) shows a preference for human and functional tool motion. VLSM analyses also revealed that damage to this right mSTS/STG region led to more severe impairment in the recognition of human and functional tool motion relative to animal motion, indicating the causal role of this brain area in human-agent motion processing. The findings for the right mSTS/STG cannot be reduced to a preference for articulated motion or processing of social variables since neither factor is involved in functional tool motion recognition. We conclude that a unidimensional biological-nonbiological distinction cannot fully explain the visual motion effects in lateral temporal cortex. Instead, the results suggest the existence of distinct components in right posterior temporal cortex and mSTS/STG that are associated, respectively, with biological motion and human-agent motion processing.

Two picture naming experiments show that compound word production in Mandarin Chinese and in English is determined by the compound's whole-word frequency, and not by its constituent morpheme frequency. Four control experiments rule out that these results are caused by recognition or articulatory processes. These results are consistent with models of lexical access that assume compounds are stored in their full-form and that frequency affects the retrieval of whole words. The present results corroborate the results from previous studies that have investigated compound word production in Mandarin Chinese, but also differ from those previously reported on compound word production in Dutch. The possibility that this inconsistency arises due to cross-linguistic, or task differences is discussed.