A touch of hierarchy: population receptive fields reveal fingertip integration in Brodmann areas in human primary somatosensory cortex.

Several neuroimaging studies have shown the somatotopy of body part representations in primary somatosensory cortex (S1), but the functional hierarchy of distinct subregions in human S1 has not been adequately addressed. The current study investigates the functional hierarchy of cyto-architectonically distinct regions, Brodmann areas BA3, BA1, and BA2, in human S1. During functional MRI experiments, we presented participants with vibrotactile stimulation of the fingertips at three different vibration frequencies. Using population Receptive Field (pRF) modeling of the fMRI BOLD activity, we identified the hand region in S1 and the somatotopy of the fingertips. For each voxel, the pRF center indicates the finger that most effectively drives the BOLD signal, and the pRF size measures the spatial somatic pooling of fingertips. We find a systematic relationship of pRF sizes from lower-order areas to higher-order areas. Specifically, we found that pRF sizes are smallest in BA3, increase slightly towards BA1, and are largest in BA2, paralleling the increase in visual receptive field size as one ascends the visual hierarchy. Additionally, we find that the time-to-peak of the hemodynamic response in BA3 is roughly 0.5 s earlier compared to BA1 and BA2, further supporting the notion of a functional hierarchy of subregions in S1. These results were obtained during stimulation of different mechanoreceptors, suggesting that different afferent fibers leading up to S1 feed into the same cortical hierarchy.

Stimulus Dependence of Gamma Oscillations in Human Visual Cortex.

A striking feature of some field potential recordings in visual cortex is a rhythmic oscillation within the gamma band (30-80 Hz). These oscillations have been proposed to underlie computations in perception, attention, and information transmission. Recent studies of cortical field potentials, including human electrocorticography (ECoG), have emphasized another signal within the gamma band, a nonoscillatory, broadband signal, spanning 80-200 Hz. It remains unclear under what conditions gamma oscillations are elicited in visual cortex, whether they are necessary and ubiquitous in visual encoding, and what relationship they have to nonoscillatory, broadband field potentials. We demonstrate that ECoG responses in human visual cortex (V1/V2/V3) can include robust narrowband gamma oscillations, and that these oscillations are reliably elicited by some spatial contrast patterns (luminance gratings) but not by others (noise patterns and many natural images). The gamma oscillations can be conspicuous and robust, but because they are absent for many stimuli, which observers can see and recognize, the oscillations are not necessary for seeing. In contrast, all visual stimuli induced broadband spectral changes in ECoG responses. Asynchronous neural signals in visual cortex, reflected in the broadband ECoG response, can support transmission of information for perception and recognition in the absence of pronounced gamma oscillations.

Sentinel lymphadenectomy accurately predicts nodal status in T2 breast cancer.

BACKGROUND: Sentinel lymph node biopsy (SLNB) has emerged as a reliable, accurate method of staging the axilla for early breast cancer. Although widely accepted for T1 lesions, its use in larger tumors remains controversial. This study was undertaken to define the role of SLNB for T2 breast cancer. STUDY DESIGN: From a prospective breast sentinel lymph node database of 1,627 patients accrued between September 1996 and November 1999, we identified 223 patients with clinical T1-2N0 breast cancer who underwent 224 lymphatic mapping procedures and SLNB followed by a standard axillary lymph node dissection (ALND). Preoperative lymphatic mapping was performed by injection of unfiltered technetium 99 sulfur colloid and isosulfan blue dye. Data about patient and tumor characteristics and the status of the sentinel lymph nodes and the axillary nodes were analyzed. Statistics were performed using Fisher's exact test. RESULTS: Two hundred four of 224 sentinel lymph node mapping procedures (91%) were successful. Median tumor size was 2.0 cm (range 0.2 to 4.8 cm). One hundred forty-five of the 204 patients had T1 lesions and 59 patients had T2 lesions. There were 92 pathologically positive axillae, 5 (5%) of which were not evident either by SLNB or by intraoperative clinical examination. The false-negative rate and accuracy were not significantly different between the two groups, but axillary node metastases were observed more frequently with T2 than with T1 tumors (p = 0.005); other factors, including patient age, prior surgical biopsy, upper-outer quadrant tumor location, and tumor lymphovascular invasion were not associated with a higher incidence of false-negative SLNB in either T1 or T2 tumors. CONCLUSIONS: SLNB is as accurate for T2 tumors as it is for T1 tumors. Because no tumor or patient characteristics predict a high false-negative rate, all patients with T1-2N0 breast cancer should be considered candidates for the procedure. Complete clinical examination of the axilla should be undertaken to avoid missing palpable axillary nodal metastases.

Whole body hyperthermia induction of soluble tumor necrosis factor receptors: implications for rheumatoid diseases.

OBJECTIVE: To test the hypothesis that 41.8 degrees C x 60 min whole body hyperthermia (WBH) induces increased serum levels of soluble necrosis factor receptors (sTNF-R). METHODS: We tested the serum of cancer patients for changes in sTNF-RI and RII levels, as a function of time, pre and post: (1) WBH alone, (2) WBH and chemotherapy, i.e., melphalan (L-PAM), and (3) L-PAM alone. RESULTS: For sTNF-RI there was a marked increase (over pre-treatment values, i.e., 86%) in serum levels after WBH alone (n = 3), which peaked 2.5 h post-WBH; L-PAM (iv) only resulted in a dip in sTNF-RI seen 40 min postadministration; the combination (WBH + L-PAM), resulted in both the dip at 40 min and the increase at 2.5 h post-treatment. For sTNF-RII both WBH alone (n = 3) and WBH + L-PAM (n = 2), there was an increase in receptor serum levels of 25% and 30%, respectively, which peaked 5.5 h post-treatment, and remained elevated at 24 h. L-PAM alone resulted in a dip in levels only at 40 min post-treatment. sTNF-RI and RII levels returned to baseline values within 7 days post-treatment. CONCLUSION: 41.8 degrees C WBH results in transient increases in TNF-RI and RII. These results may have therapeutic implications for the application of WBH to TNF mediated disease processes.