Spotting lesions in thorax X-rays at a glance: holistic processing in radiology.

Radiologists often need only a glance to grasp the essence of complex medical images. Here, we use paradigms and manipulations from perceptual learning and expertise fields to elicit mechanisms and limits of holistic processing in radiological expertise. In the first experiment, radiologists were significantly better at categorizing thorax X-rays when they were presented for 200 ms in an upright orientation than when they were presented upside-down. Medical students, in contrast, were guessing in both situations. When the presentation time was increased to 500 ms, allowing for a couple more glances, the radiologists improved their performance on the upright stimuli, but remained at the same level on the inverted presentation. The second experiment circumvented the holistic processing by immediately cueing a tissue within the X-rays, which may or may not contain a nodule. Radiologists were again better than medical students at recognizing whether the cued tissue was a nodule, but this time neither the inverted presentation nor additional time affected their performance. Our study demonstrates that holistic processing is most likely a continuous recurring process which is just as susceptible to the inversion effect as in other expertise domains. More importantly, our study also indicates that holistic-like processing readily occurs in complex stimuli (e.g., whole thorax X-rays) but is more difficult to find in uniform single parts of such stimuli (e.g., nodules).

The Faces in Radiological Images: Fusiform Face Area Supports Radiological Expertise.

The fusiform face area (FFA) has often been used as an example of a brain module that was developed through evolution to serve a specific purpose-face processing. Many believe, however, that FFA is responsible for holistic processing associated with any kind of expertise. The expertise view has been tested with various stimuli, with mixed results. One of the main stumbling blocks in the FFA controversy has been the fact that the stimuli used have been similar to faces. Here, we circumvent the problem by using radiological images, X-rays, which bear no resemblance to faces. We demonstrate that FFA can distinguish between X-rays and other stimuli by employing multivariate pattern analysis. The sensitivity to X-rays was significantly better in experienced radiologists than that in medical students with limited radiological experience. For the radiologists, it was also possible to use the patterns of FFA activations obtained on faces to differentiate X-ray stimuli from other stimuli. The overlap in the FFA activation is not based on visual similarity of faces and X-rays but rather on the processes necessary for expertise with both kinds of stimulus. Our results support the expertise view that FFA's main function is related to holistic processing.

Transcranial sonography reveals cerebellar, nigral, and forebrain abnormalities in Friedreich's ataxia.

BACKGROUND: Friedreich's ataxia (FA) is essentially characterized by degeneration of the dorsal root ganglia, the dorsal nuclei of Clarke, and the long spinal fiber tracts, yet there is accumulating evidence that neurodegeneration extends beyond these predilection sites. Transcranial sonography (TCS) has evolved as a valuable complementary neuroimaging tool in the assessment of neurodegenerative diseases due to its capacity to well depict structural changes and the accumulation of heavy metals. Its use for assessing cerebellar neurodegeneration, however, has not yet been investigated.Here we investigated whether TCS allows to assess particular features of cerebellar as well as midbrain and forebrain abnormalities in FA. METHODS: Comprehensive TCS imaging of 34 FA patients and 34 age-matched healthy controls. RESULTS: Hyperechogenicity of the dentate nucleus was very frequent in FA patients (85%) and could even be observed in patients with short disease duration, suggesting that dentate alterations are a common and probably early feature of FA. Substantia nigra was significantly hypoechogenic, possibly indicating regional changes in subcellular brain iron regulation. FA patients showed significantly enlarged 4th, 3rd, and lateral ventricles, thus corroborating earlier MRI and postmortem findings of substantial cerebellar and forebrain atrophy in FA. CONCLUSIONS: TCS provides a quick-to-apply and inexpensive in vivo assessment of both cerebellar and noncerebellar abnormalities in FA, in particular highlighting dentate hyperechogenicity as a core feature. It might serve as a promising tool for imaging aspects of cerebellar neurodegeneration also in other neurodegenerative disorders.