Visual Information Routes in the Posterior Dorsal and Ventral Face Network Studied with Intracranial Neurophysiology and White Matter Tract Endpoints.

Occipitotemporal regions within the face network process perceptual and socioemotional information, but the dynamics and information flow between different nodes of this network are still debated. Here, we analyzed intracerebral EEG from 11 epileptic patients viewing a stimulus sequence beginning with a neutral face with direct gaze. The gaze could avert or remain direct, while the emotion changed to fearful or happy. N200 field potential peak latencies indicated that face processing begins in inferior occipital cortex and proceeds anteroventrally to fusiform and inferior temporal cortices, in parallel. The superior temporal sulcus responded preferentially to gaze changes with augmented field potential amplitudes for averted versus direct gaze, and large effect sizes relative to other network regions. An overlap analysis of posterior white matter tractography endpoints (from 1066 healthy brains) relative to active intracerebral electrodes in the 11 patients showed likely involvement of both dorsal and ventral posterior white matter pathways. Overall, our data provide new insight into the timing of face and social cue processing in the occipitotemporal brain and anchor the superior temporal cortex in dynamic gaze processing.

Reliability of S.A.R.A. (sterilization and reimplantation autograft) technique in long bone open fractures.

The reimplantation of small or large extruded bone segments is one of the most complex clinical management scenarios in the treatment of open fractures. No consensus exists regarding the efficiency of this technique. The aim of the study was to analyse the clinical and radiological outcomes of Sterilization and Reimplantation Autograft (S.A.R.A.) technique in open fractures. Therefore, fifteen skeletally mature patients with Gustilo-Anderson -IIIB type fractures treated with autograft reimplantation, were included in this study. The sample size was divided in two groups: patients with a loss of small segments (Group A - less than 5 cm) and those with large segments (Group B - greater than 5 cm). Eight patients belonged to Group A and seven to Group B. The treatment of contaminated bone may be performed by the following protocols: saline rinse, povidone-iodine scrub and saline rinse, retain periosteum, immersion in antibiotic solution (clindamycin and gentamicin and metronidazole), washing with physiological solution, acute reimplantation in Group A or reimplantation after 21 days in Group B after a bone freezing at -80°C. The Radiographic Union Score (RUS), pain visual analogic score (VAS), patient satisfaction and return to work were assessed at a mean follow-up of 24 months. No cases of superficial or deep infection were reported at 2-year follow-up. The fractures achieved a complete union in 14 patients; one patient belonging to Group A had a malabsorption of the replanted bone. Furthermore, povidone-iodine scrub, antibiotic solution immersion, and washing with physiological solution preserved the articular surface morphology. This study suggests that reimplantation of extruded short or long segments may represent a reliable alternative to amputation in open long bone fractures. Further studies are needed to define the most efficient technique for sterilizing the bone autograft to reduce the complication rate.

Unlocked versus dynamic and static distal locked femoral nails in stable and unstable intertrochanteric fractures. A prospective study.

INTRODUCTION: Few clinical studies have analyzed the utility of distal interlocking screws in stable and unstable intertrochanteric fractures treated with intramedullary devices. We performed a prospective analysis comparing short unlocked versus short dynamic and short static distal locked intramedullary nails. MATERIALS AND METHODS: Nine level-II trauma centres were involved in the study. 240 patients over the age of 65 with a stable (AO/OTA 31-A1) or unstable intertrochanteric fracture (AO/OTA 31-A2) were prospectively investigated. The same type of nail was used in every patient. Patients were randomly divided into 3 groups according to the type of distal locking used. Intra-operative variables were examined and patients were followed clinically and radiographically at 1, 3, 6, 12 months postoperatively. All complications were recorded. RESULTS: A total of 212 patients completed 1 year of follow-up visits. In the Unlocking Group (UG) the operation time, blood loss, fluoroscopy time, total length of incision were significantly decreased compared to both the Dynamic Group (DG) and the Static Group (SG) (p < 0.05). Conversely, no reliable differences in intraoperative variables were noted between the Dynamic Group and the Static Group (p > 0.05). In terms of time of fracture union we found no differences among the three Groups (p > 0.05). Moreover, no cases of limb shortening >1 cm or varus collapse were detected in any group. The 3 Groups were similar in terms of HHS, SF-12 and Barthel index results at 1-year follow-up (p > 0.05). Finally, no significant differences were demonstrated across the three Groups in terms of major complications. CONCLUSIONS: This clinical study further confirms the hypothesis that short intramedullary nails do not need to be locked for stable and unstable intertrochanteric fractures.

Is distal locking with short intramedullary nails necessary in stable pertrochanteric fractures? A prospective, multicentre, randomised study.

We investigated whether a proximal femoral nail can be implanted without a distal locking screw in AO/OTA 31-A1 and 31-A2 pertrochanteric stable femur fractures. A multicentre, randomised study was conducted in six level-two trauma centres in our area (Puglia, Italy). A total of 333 patients received their allocated intervention (162 in the locking group [LG] and 171 in the unlocking group [UG]) and 266 patients were included in the final analysis at 1year. Our data showed no statistically significant difference between the two groups at 1-year follow-up for ability to walk, SF-36 questionnaire results, residual pain (visual analogue scale [VAS] score) and level of overall satisfaction. There were also no statistically significant differences between groups for mortality and length of hospital stay. Conversely, the UG was associated with shorter operation and fluoroscopy times, shorter surgical incision length, and less blood loss and residual thigh pain. Pertrochanteric stable fractures (31-A1, 31-A2) can be treated successfully with intramedullary nails without distal locking, reducing patient and clinical personnel radiation exposure and sanitary costs (surgery time and screws costs).

Cortical hyperexcitability in progressive myoclonus epilepsy: a study with transcranial magnetic stimulation.

In progressive myoclonus epilepsy (PME), responses to afferent input are frequently abnormal. It is unclear whether the abnormality lies at the cortical, subcortical, or segmental level. To obtain evidence for an exaggerated effect on motor cortical excitability, we used peripheral nerve and transcranial magnetic stimulation in controls and subjects with idiopathic generalized epilepsy and PME. Mean threshold intensity was higher in those with idiopathic generalized epilepsy and PME than in controls, probably as a result of anticonvulsant treatment. A long-latency response to peripheral stimulation and an exaggerated facilitatory effect of peripheral stimulation on the motor evoked potential was present in subjects with PME. Latency differences between the late responses in the upper and lower limbs provided evidence against a segmental reflex and implicated rapidly conducting fibers in the spinal cord. Both the late response and the facilitatory effect had onset latencies consistent with a transcortical pathway, suggesting an exaggerated effect of afferent input on motor cortical excitability in PME.

Reemergence of activation with poststroke somatosensory recovery: a serial fMRI case study.

The authors demonstrate the potential for poststroke return of activation in regions normally involved in touch discrimination in a serial, whole-brain fMRI study of a patient with marked sensory loss followed by good recovery. A return of activation in ipsilesional primary and bilateral secondary somatosensory cortices was observed at 3 months after stroke and was maintained at 6 months, indicating a reemergence of activation after the interval of somatosensory recovery. There was little evidence of neural plastic changes early after stroke (2 weeks), when sensory loss was severe.

Post-ictal recognition memory predicts laterality of temporal lobe seizure focus: comparison with post-operative data.

Standardized verbal and visuo-spatial memory recognition were obtained on 15 patients with unilateral temporal lobe epilepsy (TLE), using a reference group of 43 (12 males, 31 females) subjects with no previous history of neurological disease. Inter-ictal measures on these two tasks failed to differentiate between those patients with left vs right seizure foci. When eight of these patients were tested post-ictally (within 1 hr of seizure), seven showed the expected selective memory impairment when compared to inter-ictal performance. Left TLE patients showed a relative lowering of verbal memory, whereas patients with right TLE showed a relative visuo-spatial memory impairment. A similar result was also found in the patients when a comparison between pre-operative (inter-ictal) and post-operative performance was made, thereby further substantiating the validity of the tasks. This significant association between side of seizure focus and selective impairment of post-ictal memory performance provides evidence of a more direct method of neuropsychological diagnosis in TLE patients prior to surgery.

The spatiotemporal dynamics of the face inversion effect: a magneto- and electro-encephalographic study.

The neurophysiological basis of the face inversion effect was studied with magneto- and electro-encephalography in 10 normal subjects. Spatiotemporal analyses using dipole modeling was performed on combined evoked magneto and electro-encephalography data to hemifield presentation of upright and inverted faces and objects. Inferior temporal cortex, i.e. fusiform gyrus, and lateral temporal cortex near the superior temporal sulcus were activated simultaneously, but independently, at 140-200 ms post-stimulus to upright and inverted unfamiliar faces. Right hemisphere inferior temporal cortex and lateral temporal cortex were active in all subjects, and in the left hemisphere in half the subjects. Latencies to inverted relative to upright faces were longer in the right hemisphere, and shorter in the left hemisphere. For right hemifield stimulation ipsilateral activation delay was around 18-19 ms for both upright and inverted faces and was calculated from all 10 subjects. For left hemifield stimulation, and the data from 7 of 10 subjects, it was 22 and 29 ms to upright and inverted faces, respectively. In sum, the methods used in this study did not identify clear differences in anatomical location of activated regions to upright and inverted faces. We believe, however, that the differences in processing upright versus inverted faces are attributable to temporal processing differences rather than to processing of information by different brain regions.

Comparative assessment of sensorimotor function using functional magnetic resonance imaging and electrophysiological methods.

Accurate assessment of the location of the sensorimotor cortex is important in presurgical investigation of and planning for patients with lesions impinging on this region. In this review, the relationship between the assessment of sensorimotor cortex by invasive electrophysiological mapping and functional magnetic resonance imaging (fMRI) is discussed. A number of areas are covered: (a) brief backgrounds of MRI and fMRI are provided, (b) existing fMRI literature of sensorimotor cortex activation is surveyed, (c) results of fMRI sensorimotor studies and intracranial somatosensory evoked potential (SEP) recordings and cortical stimulation in neurosurgical patients are compared, and (d) the locus of fMRI activation is discussed in the light of cortical generators of SEP components.

Functional magnetic resonance imaging of sensory and motor cortex: comparison with electrophysiological localization.

Functional magnetic resonance (MR) imaging was performed using a 1.5-tesla MR system to localize sensorimotor cortex. Six neurologically normal subjects were studied by means of axial gradient-echo images with a motor task and one or more sensory tasks: 1) electrical stimulation of the median nerve; 2) continuous brushing over the thenar region; and 3) pulsed flow of compressed air over the palm and digits. An increased MR signal was observed in or near the central sulcus, consistent with the location of primary sensory and motor cortex. Four patients were studied using echo planar imaging sequences and motor and sensory tasks. Three patients had focal refractory seizures secondary to a lesion impinging on sensorimotor cortex. Activation seen on functional MR imaging was coextensive with the location of the sensorimotor area determined by evoked potentials and electrical stimulation. Functional MR imaging provides a useful noninvasive method of localization and functional assessment of sensorimotor cortex.

Scalp and limbic P3 event-related potentials in the assessment of patients with temporal lobe epilepsy.

Auditory oddball scalp and limbic P3s were recorded from 18 patients with unilateral temporal lobe epilepsy (TLE) prior to seizure surgery. Limbic P3s were unilaterally absent ipsilateral to the seizure focus and were present in the nonepileptogenic temporal lobe in all 18 cases studied. Scalp P3s, recorded from C3 and C4, on the other hand, were elicited bilaterally and there was no significant difference in amplitude or latency between the epileptogenic and nonepileptogenic sides. These data concur with studies of scalp P3 performed following surgery and suggest that the assessment of the contribution of limbic P3 to scalp P3 may be masked by volume conduction effects and other generators of P3. We conclude that the P3 recorded from central scalp sites, unlike its limbic counterpart, offers little clinical information in the presurgical assessment of patients with TLE.

Occipitotemporal activity elicited by viewing eye movements: a magnetoencephalographic study.

The temporal and spatial processing of viewing eye movements was studied by magnetoencephalography (MEG) in six normal subjects. Three visual stimulus types were studied: (1) moving eyes (EYES), (2) moving simulated eyes (SIM), consisting of checks moving in the same spatial location as EYES, and (3) an inwardly moving radial pattern (RADIAL). A large clear MEG component, 1M, with mean peak latency of approximately 170 ms, was seen in the right hemisphere to RADIAL and EYES in all six subjects. The 1M to EYES was significantly longer in latency and smaller in amplitude than that seen to RADIAL. A left hemisphere 1M to EYES and RADIAL was seen in three of six subjects. In all subjects and both hemispheres the equivalent current dipoles (ECD) for EYES and RADIAL were located near the occipitotemporal border, the MT/V5 homologue in humans. The ECD to EYES was significantly more posterior and inferior than that to RADIAL, with a calculated significant separation distance of around 1 cm. No ECD was estimated in the fusiform gyrus, a structure that plays a main role in static face perception. Although the 1M was detected in SIM in all six subjects, our criteria for a reliable ECD could only be satisfied in only one subject. Our results suggest that the cortex of human MT/V5 and its surrounds is active both in the perception of eye motion and motion in general, particularly in the right hemisphere. The areas responsive to eye motion were separable from those responsive to radial motion. These data suggest that there may be specialization within regions of human cortex previously thought to be sensitive to motion in general.

Erps evoked by viewing facial movements.

Human neuroimaging and event-related potential (ERP) studies suggest that ventral and lateral temporo-occipital cortex is sensitive to static faces and face parts. Recent fMRI data also show activation by facial movements. In this study we recorded from 22 posterior scalp locations in 20 normal right-handed males to assess ERPs evoked by viewing: (1) moving eyes and mouths in the context of a face; (2) moving and static eyes with and without facial context. N170 and P350 peak amplitude and latency data were analysed. N170 is an ERP previously shown to be preferentially responsive to face and eye stimuli, and P350 immediately follows N170. Major results were: (1) N170 was significantly larger over the bilateral temporal scalp to viewing opening mouths relative to closing mouths, and to eye aversion relative to eyes gazing at the observer; (2) at a focal region over the right inferior temporal scalp, N170 was significantly earlier to mouth opening relative to closing, and to eye aversion relative to eyes gazing at the observer; (3) the focal ERP effect of eye aversion occurred independent of facial context; (4) these differences cannot be attributable to movement per se, as they did not occur in a control condition in which checks moved in comparable areas of the visual field; (5) isolated static eyes produced N170s that were not significantly different from N170s to static full faces over the right inferior temporal scalp, unlike in the left hemisphere where face N170s were significantly larger than eye N170s; (6) unlike N170, P350 exhibited nonspecific changes as a function of stimulus movement. These results suggest that: (1) bilateral temporal cortex forms part of a system sensitive to biological motion, of which facial movements form an important subset; (2) there may be a specialised system for facial gesture analysis that provides input for neuronal circuitry dealing with social attention and the actions of others.

Scalp and intracerebral P300 in surgery for temporal lobe epilepsy.

We have studied the scalp and intracerebral recordings of 12 patients with intractable temporal lobe epilepsy. The intracerebral P300 provides useful diagnostic information regarding the epileptogenicity of a temporal lobe. The scalp P300, by nature of its bilateral scalp distribution, is unable to be used diagnostically in assessing candidates for possible anterior temporal lobectomy.

Electrophysiological studies of human face perception. III: Effects of top-down processing on face-specific potentials.

This is the last in a series of papers dealing with intracranial event-related potential (ERP) correlates of face perception. Here we describe the results of manipulations that may exert top-down influences on face recognition and face-specific ERPs, and the effects of cortical stimulation at face-specific sites. Ventral face-specific N200 was not evoked by affective stimuli; showed little or no habituation; was not affected by the familiarity or unfamiliarity of faces; showed no semantic priming; and was not affected by face-name learning or identification. P290 and N700 were affected by semantic priming and by face-name learning and identification. The early fraction of N700 and face-specific P350 exhibited significant habituation. About half of the AP350 sites exhibited semantic priming, whereas the VP350 and LP350 sites did not. Cortical stimulation evoked a transient inability to name familiar faces or evoked face-related hallucinations at two-thirds of face-specific N200 sites. These results are discussed in relation to human behavioral studies and monkey single-cell recordings. Discussion of results of all three papers concludes that: face-specific N200 reflects the operation of a module specialized for the perception of human faces; ventral and lateral occipitotemporal cortex are composed of a complex mosaic of functionally discrete patches of cortex of variable number, size and location; in ventral cortex there is a posterior-to-anterior trend in the location of patches in the order letter-strings, form, hands, objects, faces and face parts; P290 and N700 at face-specific N200 sites, and face-specific P350, are subject to top-down influences.

Face-sensitive regions in human extrastriate cortex studied by functional MRI.

1. We have previously identified face-selective areas in the mid-fusiform and inferior temporal gyri in electrophysiological recordings made from chronically implanted subdural electrodes in epilepsy patients. In this study, functional magnetic resonance imaging (fMRI) was used to study the anatomic extent of face-sensitive brain regions and to assess hemispheric laterality. 2. A time series of 128 gradient echo echoplanar images was acquired while subjects continuously viewed an alternating series of 10 unfamiliar faces followed by 10 equiluminant scrambled faces. Each cycle of this alternating sequence lasted 12 s and each experimental run consisted of 14 cycles. The time series of each voxel was transformed into the frequency domain using Fourier analysis. Activated voxels were defined by significant peaks in their power spectra at the frequency of stimulus alternation and by a 180 degrees phase shift that followed changes in stimulus alternation order. 3. Activated voxels to faces were obtained in the fusiform and inferior temporal gyri in 9 of 12 subjects and were approximately coextensive with previously identified face-selective regions. Nine subjects also showed activation in the left or right middle occipital gyri, or in the superior temporal or lateral occipital sulci. Cortical volumes activated in the left and right hemispheres were not significantly different. Activated voxels to scrambled faces were observed in six subjects at locations mainly in the lingual gyri and collateral sulci, medial to the regions activated by faces. 4. Face stimuli activated portions of the midfusiform and inferior temporal gyri, including adjacent cortex within occipitotemporal sulci.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative effects of age on limbic and scalp P3.

We studied the effects of age on the limbic and scalp P3 in 45 patients with intracranial electrodes implanted for pre-surgical investigation of focal seizures. Scalp P3 data from a reference group of 24 healthy control subjects were also analyzed for comparison. An auditory oddball paradigm with infrequent stimuli being presented with a probability of 0.20 was used. In normals P3 latency increased by 1.34 msec/year (r = 0.60, P less than 0.01). In the patients limbic and scalp P3 latency increased linearly as a function of increasing age at a rates of 3.85 msec/year (r = 0.58, P less than 0.001) and 2.71 msec/year (r = 0.56, P less than 0.01), respectively. The rate of increase of P3 latency with age was significantly lower in the normal controls, as compared to both the patient scalp (t = 1.79, P less than 0.05) and depth (t = 2.25, P less than 0.005) ERP data. There was no significant difference between the slopes of the patient P3 latency versus age scalp and depth data (t = 1.09, P greater than 0.1). Unlike for normal controls, there was no relationship between age and limbic P3 amplitude (r = 0.02, P greater than 0.1) or age and scalp P3 amplitude (r = 0.17, P greater than 0.1). The differences between controls and patients could be due to: (i) effects of chronic seizures; (ii) long-term effects of anticonvulsant use; (iii) the use of a relatively long inter-stimulus interval which may have selectively affected the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Face-specific processing in the human fusiform gyrus.

The perception of faces is sometimes regarded as a specialized task involving discrete brain regions. In an attempt to identi$ face-specific cortex, we used functional magnetic resonance imaging (fMRI) to measure activation evoked by faces presented in a continuously changing montage of common objects or in a similar montage of nonobjects. Bilateral regions of the posterior fusiform gyrus were activated by faces viewed among nonobjects, but when viewed among objects, faces activated only a focal right fusiform region. To determine whether this focal activation would occur for another category of familiar stimuli, subjects viewed flowers presented among nonobjects and objects. While flowers among nonobjects evoked bilateral fusiform activation, flowers among objects evoked no activation. These results demonstrate that both faces and flowers activate large and partially overlapping regions of inferior extrastriate cortex. A smaller region, located primarily in the right lateral fusiform gyrus, is activated specifically by faces.

Electrophysiological studies of human face perception. I: Potentials generated in occipitotemporal cortex by face and non-face stimuli.

This and the following two papers describe event-related potentials (ERPs) evoked by visual stimuli in 98 patients in whom electrodes were placed directly upon the cortical surface to monitor medically intractable seizures. Patients viewed pictures of faces, scrambled faces, letter-strings, number-strings, and animate and inanimate objects. This paper describes ERPs generated in striate and peristriate cortex, evoked by faces, and evoked by sinusoidal gratings, objects and letter-strings. Short-latency ERPs generated in striate and peristriate cortex were sensitive to elementary stimulus features such as luminance. Three types of face-specific ERPs were found: (i) a surface-negative potential with a peak latency of approximately 200 ms (N200) recorded from ventral occipitotemporal cortex, (ii) a lateral surface N200 recorded primarily from the middle temporal gyrus, and (iii) a late positive potential (P350) recorded from posterior ventral occipitotemporal, posterior lateral temporal and anterior ventral temporal cortex. Face-specific N200s were preceded by P150 and followed by P290 and N700 ERPs. N200 reflects initial face-specific processing, while P290, N700 and P350 reflect later face processing at or near N200 sites and in anterior ventral temporal cortex. Face-specific N200 amplitude was not significantly different in males and females, in the normal and abnormal hemisphere, or in the right and left hemisphere. However, cortical patches generating ventral face-specific N200s were larger in the right hemisphere. Other cortical patches in the same region of extrastriate cortex generated grating-sensitive N180s and object-specific or letter-string-specific N200s, suggesting that the human ventral object recognition system is segregated into functionally discrete regions.