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).

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.

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.

Human neural responses elicited to observing the actions of others.

Monkey electrophysiological and human neuroimaging studies indicate the existence of specialized neural systems for the perception and execution of actions. To date, the dynamics of these neural systems in humans have not been well studied. Here, we investigated the spatial and temporal behavior of human neural responses elicited to viewing motion of the face, hand, and body. Scalp event-related potentials (ERPs) were recorded in 20 participants viewing videotaped mouth (opening, closing), hand (closing, opening), and body stepping (forward, backward) movements. ERP peak differences within the movements of each body part were compared using topographical maps of voltage, voltage difference, and Student's t-test at ERP peak latencies. Predominantly temporoparietal negative ERPs occurred to motion of all body parts within 200 ms postmovement onset. Hand closure elicited a significantly greater negativity than opening, particularly in the left hemisphere. Vertex positive ERPs within 300 ms postmovement onset were elicited to hand and body motion. A significantly greater positivity occurred for the body stepping forward relative to stepping backward. The ERP topography was consistent with observed activation foci in human neuroimaging studies. Our data indicate that the neural activity of a system dedicated to the perception of high-level motion stimuli can rapidly differentiate between movements across and within body parts.

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.

Social perception from visual cues: role of the STS region.

Social perception refers to initial stages in the processing of information that culminates in the accurate analysis of the dispositions and intentions of other individuals. Single-cell recordings in monkeys, and neurophysiological and neuroimaging studies in humans, reveal that cerebral cortex in and near the superior temporal sulcus (STS) region is an important component of this perceptual system. In monkeys and humans, the STS region is activated by movements of the eyes, mouth, hands and body, suggesting that it is involved in analysis of biological motion. However, it is also activated by static images of the face and body, suggesting that it is sensitive to implied motion and more generally to stimuli that signal the actions of another individual. Subsequent analysis of socially relevant stimuli is carried out in the amygdala and orbitofrontal cortex, which supports a three-structure model proposed by Brothers. The homology of human and monkey areas involved in social perception, and the functional interrelationships between the STS region and the ventral face area, are unresolved issues.

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.

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.

Electrophysiological studies of human face perception. II: Response properties of face-specific potentials generated in occipitotemporal cortex.

In the previous paper the locations and basic response properties of N200 and other face-specific event-related potentials (ERPs) were described. In this paper responsiveness of N200 and related ERPs to the perceptual features of faces and other images was assessed. N200 amplitude did not vary substantially, whether evoked by colored or grayscale faces; normal, blurred or line-drawing faces; or by faces of different sizes. Human hands evoked small N200s at face-specific sites, but evoked hand-specific ERPs at other sites. Cat and dog faces evoked N200s that were 73% as large as to human faces. Hemifield stimulation demonstrated that the right hemisphere is better at processing information about upright faces and transferring it to the left hemisphere, whereas the left hemisphere is better at processing information about inverted faces and transferring it to the right hemisphere. N200 amplitude was largest to full faces and decreased progressively to eyes, face contours, lips and noses viewed in isolation. A region just lateral to face-specific N200 sites was more responsive to internal face parts than to faces, and some sites in ventral occipitotemporal cortex were face-part-specific. Faces with eyes averted or closed evoked larger N200s than those evoked by faces with eyes forward. N200 amplitude and latency were affected by the joint effects of eye and head position in the right but not in the left hemisphere. Full and three-quarter views of faces evoked larger N200s than did profile views. The results are discussed in relation to behavioral studies in humans and single-cell recordings in monkeys.

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.

Dissociation of mnemonic and perceptual processes during spatial and nonspatial working memory using fMRI.

Neuroimaging studies in humans have consistently found robust activation of frontal, parietal, and temporal regions during working memory tasks. Whether these activations represent functional networks segregated by perceptual domain is still at issue. Two functional magnetic resonance imaging experiments were conducted, both of which used multiple-cycle, alternating task designs. Experiment 1 compared spatial and object working memory tasks to identify cortical regions differentially activated by these perceptual domains. Experiment 2 compared working memory and perceptual control tasks within each of the spatial and object domains to determine whether the regions identified in experiment 1 were driven primarily by the perceptual or mnemonic demands of the tasks, and to identify common brain regions activated by working memory in both perceptual domains. Domain-specific activation occurred in the inferior parietal cortex for spatial tasks, and in the inferior occipitotemporal cortex for object tasks, particularly in the left hemisphere. However, neither area was strongly influenced by task demands, being nearly equally activated by the working memory and perceptual control tasks. In contrast, activation of the dorsolateral prefrontal cortex and the intraparietal sulcus (IPS) was strongly task-related. Spatial working memory primarily activated the right middle frontal gyrus (MFG) and the IPS. Object working memory activated the MFG bilaterally, the left inferior frontal gyrus, and the IPS, particularly in the left hemisphere. Finally, activation of midline posterior regions, including the cingulate gyrus, occurred at the offset of the working memory tasks, particularly the shape task. These results support a prominent role of the prefrontal and parietal cortices in working memory, and indicate that spatial and object working memory tasks recruit differential hemispheric networks. The results also affirm the distinction between spatial and object perceptual processing in dorsal and ventral visual pathways.

Temporal cortex activation in humans viewing eye and mouth movements.

We sought to determine whether regions of extrastriate visual cortex could be activated in subjects viewing eye and mouth movements that occurred within a stationary face. Eleven subjects participated in three to five functional magnetic resonance imaging sessions in which they viewed moving eyes, moving mouths, or movements of check patterns that occurred in the same spatial location as the eyes or mouth. In each task, the stimuli were superimposed on a radial background pattern that continually moved inward to control for the effect of movement per se. Activation evoked by the radial background was assessed in a separate control task. Moving eyes and mouths activated a bilateral region centered in the posterior superior temporal sulcus (STS). The moving check patterns did not appreciably activate the STS or surrounding regions. The activation by moving eyes and mouths was distinct from that elicited by the moving radial background, which primarily activated the posterior-temporal-occipital fossa and the lateral occipital sulcus-a region corresponding to area MT/V5. Area MT/V5 was also strongly activated by moving eyes and to a lesser extent by other moving stimuli. These results suggest that a superior temporal region centered in the STS is preferentially involved in the perception of gaze direction and mouth movements. This region of the STS may be functionally related to nearby superior temporal regions thought to be involved in lip-reading and in the perception of hand and body movement.

Comparison of cortical activation evoked by faces measured by intracranial field potentials and functional MRI: two case studies.

The localization of neural processes contributing to face perception was studied in two patients using event-related field potentials (ERPs) recorded from subdural strips and functional magnetic resonance imaging (fMRI). Despite the differences in the physiological bases of the two techniques, and in the tasks used to elicit activation, good correspondence was obtained in the anatomical patterns of activation. Face-specific ERPs (N200s) and fMRI activation by faces occurred at the same locations in the right ventral extrastriate region of both patients, and in a similar region of the left hemisphere of one patient. Some discrepancies were noted in the pattern of activation which may reflect the adequacy of the tasks in identifying face-specific as opposed to face-sensitive processing, and in the differential sensitivity of the methods to the temporal course of face processing.

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.

Differential sensitivity of human visual cortex to faces, letterstrings, and textures: a functional magnetic resonance imaging study.

Twelve normal subjects viewed alternating sequences of unfamiliar faces, unpronounceable nonword letterstrings, and textures while echoplanar functional magnetic resonance images were acquired in seven slices extending from the posterior margin of the splenium to near the occipital pole. These stimuli were chosen to elicit initial category-specific processing in extrastriate cortex while minimizing semantic processing. Overall, faces evoked more activation than did letterstrings. Comparing hemispheres, faces evoked greater activation in the right than the left hemisphere, whereas letterstrings evoked greater activation in the left than the right hemisphere. Faces primarily activated the fusiform gyrus bilaterally, and also activated the right occipitotemporal and inferior occipital sulci and a region of lateral cortex centered in the middle temporal gyrus. Letterstrings primarily activated the left occipitotemporal and inferior occipital sulci. Textures primarily activated portions of the collateral sulcus. In the left hemisphere, 9 of the 12 subjects showed a characteristic pattern in which faces activated a discrete region of the lateral fusiform gyrus, whereas letterstrings activated a nearby region of cortex within the occipitotemporal and inferior occipital sulci. These results suggest that different regions of ventral extrastriate cortex are specialized for processing the perceptual features of faces and letterstrings, and that these regions are intermediate between earlier processing in striate and peristriate cortex, and later lexical, semantic, and associative processing in downstream cortical regions.

Activation of human prefrontal cortex during spatial and nonspatial working memory tasks measured by functional MRI.

Separate working memory domains for spatial location, and for objects, faces, and patterns, have been identified in the prefrontal cortex (PFC) of nonhuman primates. We have used functional magnetic resonance imaging to examine whether spatial and nonspatial visual working memory processes are similarly dissociable in human PFC. Subjects performed tasks which required them to remember either the location or shape of successive visual stimuli. We found that the mnemonic component of the working memory tasks affected the hemispheric pattern of PFC activation. The spatial (LOCATION) working memory task preferentially activated the middle frontal gyrus (MFG) in the right hemisphere, while the nonspatial (SHAPE) working memory task activated the MFG in both hemispheres. Furthermore, the area of activation in the left hemisphere extended into the inferior frontal gyrus for nonspatial SHAPE task. A perceptual target (DOT) detection task also activated the MFG bilaterally, but at a level approximately half that of the working memory tasks. The activation in the MFG occurred within 3-6 s of task onset and declined following task offset. Time-course analysis revealed a different pattern for cingulate gyrus, in which activation occurred upon task completion. Cingulate gyrus activation was greatest following the SHAPE task and was greater in the left hemisphere. The present results support the prominent role of the PFC and, specifically, the MFG in working memory, and indicate that the mnemonic content of the task affects the relative weighting of hemispheric activation.