Familiarity, spatial frequency and task determinants in processing laterally presented representations of faces

Which components of famous people recognition are lateralized? A study of face, voice and name recognition disorders in patients with neoplastic or degenerative damage of the right or left anterior temporal lobes

We administered to large groups of patients with neoplastic or degenerative damage affecting the right or left ATL, the 'Famous People Recognition Battery' (FPRB), in which subjects are required to recognize the same 40 famous people through their faces, voices and names, to clarify which components of famous people recognition are lateralized. At the familiarity level, we found, as expected, a dissociation between a greater impairment of patients with right ATL lesions on the non-verbal (face and voice) recognition modalities and of those with left ATL lesions on name familiarity. Equally expected were results obtained at the naming level, because the worse naming scores for faces and voices were observed in left-sided patients. Less foregone were, for two reasons, results obtained at the semantic level. First, no difference was found between the two hemispheric groups when scores obtained on the verbal (name) and non-verbal (face and voice) recognition modalities were account for. Second, the face and voice recognition modalities showed a different degree of right lateralization. All groups of patients showed, indeed, both at the familiarity and at the semantic level, a greater difficulty in the recognition of voices regarding faces, but this difference reached significance only in patients with right ATL lesions, suggesting a greater right lateralization of the more complex task of voice recognition. A model aiming to explain the greater right lateralization of the more perceptually demanding voice modality of person recognition is proposed.

Effects of familiarity on spatial frequency thresholds for face matching

We examined whether familiarity with a face influences the spatial frequencies (SFs) required for face matching. Using the psychophysical method of constant stimuli and a 3AFC simultaneous matching paradigm, we obtained SF thresholds for familiar- and unfamiliar-face matching from fourteen observers, of which four were personally familiar with a subset of the faces while the remainder served as controls. SF thresholds from the lower extreme of the spectrum were approximately one octave lower for familiar than for unfamiliar faces, while SF thresholds from the upper extreme of the spectrum were approximately a third of an octave higher. These results highlight a quantitative difference between processing familiar and unfamiliar faces.

Laterality in Familiar Face Recognition

An extensive series of experiments has recently led to the hypothesis that face recognition, which had been considered a right-hemisphere specialization, may actually be bilaterally processed in the two hemispheres. In the present study an attempt was made to solve the conundrum of the laterality of face recognition by performing a meta-analysis on studies of familiar face recognition. Results of six studies measuring reaction time of familiar face naming and of eleven studies measuring accuracy of familiar face naming were transformed to standard Z scores. The average Z scores for reaction time and for accuracy were then tested for their significance. The results suggested that face recognition is not lateralized. This conclusion is consistent with theories of bihemispheric cognitive resources and with the latest brain-imaging data.

Face familiarity feelings, the right temporal lobe and the possible underlying neural mechanisms

A comprehensive review was made of the relationships between right hemisphere and face familiarity feelings, taking separately into account: (a) studies of patients with unilateral lesions of the anterior or the posterior parts of the right and left temporal lobes, who showed a familiar people recognition disorder, (b) studies of right and left brain-damaged patients, presenting an increased familiarity for unknown persons or abnormal familiarity feelings for well known people, (c) results of studies conducted in normal subjects to evaluate the lateralization of face familiarity feelings. In this last section, we separately reviewed: results obtained by means of separate presentation of familiar and unfamiliar faces to the right and left visual fields; lateralization of event-related potentials evoked by familiar vs unfamiliar faces; results of activation studies presenting familiar and unfamiliar faces. Taken together, results of this review have shown that face familiarity feelings are specifically generated by the right hemisphere. Clinical and neurophysiological data suggest that familiarity feelings: (1) are probably due to a lateralized subcortical route, allowing a first, unconscious, global recognition of familiar faces and (2) facilitate the subsequent distinction of known faces (unconsciously detected) from unfamiliar faces. Results of the review have also shown that the right frontal areas play an important role in the production or monitoring of inappropriate familiarity decisions.

Left hemisphere specialization for response to positive emotional expressions: A divided output methodology

An extensive literature credits the right hemisphere with dominance for processing emotion. Conflicting literature finds left hemisphere dominance for positive emotions. This conflict may be resolved by attending to processing stage. A divided output (bimanual) reaction time paradigm in which response hand was varied for emotion (angry; happy) in Experiments 1 and 2 and for gender (male; female) in Experiment 3 focused on response to emotion rather than perception. In Experiments 1 and 2, reaction time was shorter when right-hand responses indicated a happy face and left-hand responses an angry face, as compared to reversed assignment. This dissociation did not obtain with incidental emotion (Experiment 3). Results support the view that response preparation to positive emotional stimuli is left lateralized.

A serial test of the laterality of familiar face recognition

The purpose of the present study was to address the issue of laterality of familiar face recognition. Seventy-two participants judged familiar faces presented laterally or centrally for their "faceness," familiarity, occupation, and name (which represent four stages of familiar face processing) using one of three response modes-verbal, manual, or combined. The pattern of reaction times (RTs) implied a serial process of familiar face recognition. Centrally presented stimuli were recognized faster than laterally presented stimuli. No RT differences were found between the left and right visual fields (VFs) across all judgments and response modes. The findings were interpreted as supporting the notion that there are no significant hemispheric differences in familiar face recognition.

Personal relevance and the human right hemisphere

Brain damage can selectively disrupt or distort information and ability across the range of human behaviors. One domain that has not been considered as an independent attribute consists of acquisition and maintenance of personal relevant entities such as "familiar" faces, persons, voices, names, linguistic expressions, handwriting, topography, and so on. In experimental studies of normal mentation, personal relevance is revealed in studies of emotion, arousal, affect, preference and familiarity judgments, and memory. Following focal brain damage, deficits and distortions in the experience of personal relevance, as well as in recognizing formerly personally relevant phenomena, are well known to occur. A review and interpretation of these data lead to a proposal that the right hemisphere has a special role in establishing, maintaining, and processing personally relevant aspects of the individual's world.

Hemispheric asymmetry in the processing of absolute versus relative spatial frequency

Observers indicated whether a stimulus presented to one visual field or the other consisted of two sine-wave gratings (the baseline stimulus) or those same two gratings with the addition of a 2 cycle per degree (cpd) component. When the absolute spatial frequencies of the baseline stimulus were low (0.5 and 1.0 cpd), there was a left visual field-right hemisphere (LVF-RH) advantage in reaction time (RT) to respond to the baseline stimulus which disappeared when the 2 cpd component was added (i.e., the stimulus consisted of 0.5, 1.0, and 2.0 cpd components). When the absolute spatial frequencies of the baseline stimulus were moderate to high (4.0 and 8.0 cpd), a right visual field-left hemisphere advantage in RT to respond to the baseline stimulus approached significance and shifted to a significant LVF-RH advantage when the 2 cpd component was added (i.e., the stimulus consisted of 2.0, 4.0, and 8.0 cpd components. That is, adding the same 2 cpd component caused opposite shifts in visual laterality depending on whether 2 cpd was a relatively high or relatively low frequency compared to the baseline.

Hemispheric local/global processing revisited

Hemispheric differences for local and global processing were assessed with square and rectangular stimulus shapes which contained either squares or rectangles within them. Experiment 1 manipulated the overall size and area of the stimulus items, while experiment 2 kept stimulus area constant and manipulated the number of shapes inside the stimulus. In different conditions subjects judged whether the inside shapes (local processing) or whether the outside shapes (global processing) were squares or rectangles. Reaction time measures revealed that hemispheric differences were unrelated to the local or global processing requirements as well as the spatial frequency of the stimulus texture. A left hemisphere advantage generally was obtained across stimulus and processing conditions, with the pattern of task effects dependent on the specific stimuli employed. The results suggest that the overall stimulus shape rather than processing mode or specific spatial frequency is a primary determinant of hemispheric differences for visual information.

Effects of luminance and blur on hemispheric asymmetries in temporal integration

A task involving temporal integration of form was employed to examine the effects of input characteristics on hemispheric asymmetries. In Experiment 1, decreases in luminance produced greater improvement of right hemisphere (RH) performance. In Experiment 2, dioptric blur produced greater impairment of left hemisphere (LH) performance. The results suggest that spatial frequencies below nine cycles per degree are processed more efficiently in the RH. In Experiment 3, effects of input characteristics on hemispheric asymmetry were found to be dependent on the spatial frequencies required for processing by task demands, as mediated by interflash interval (IFI) duration. Increased blur produced greater impairment of LH performance at short IFI duration; at a longer IFI duration, however, increased blur produced equal impairment of RH and LH performance.

Hemispheric differences in visual search of simple line arrays

The effects of perceptual organization on hemispheric visual-information processing were assessed with stimulus arrays composed of short lines arranged in columns. A visual-search task was employed in which subjects judged whether all the lines were vertical (same) or whether a single horizontal line was present (different). Stimulus-display organization was manipulated in two experiments by variation of line density, linear organization, and array size. In general, left-visual-field/right-hemisphere presentations demonstrated more rapid and accurate responses when the display was perceived as a whole. Right-visual-field/left-hemisphere superiorities were observed when the display organization coerced assessment of individual array elements because the physical qualities of the stimulus did not effect a gestalt whole. Response times increased somewhat with increases in array size, although these effects interacted with other stimulus variables. Error rates tended to follow the reaction-time patterns. The results suggest that laterality differences in visual search are governed by stimulus properties which contribute to, or inhibit, the perception of a display as a gestalt. The implications of these findings for theoretical interpretations of hemispheric specialization are discussed.

Perceptual characteristics in visual laterality research

Visual laterality experiments from the last three decades are reviewed. The criterion for inclusion was the independent manipulation within a constant task paradigm of one or more of the following perceptual parameters: retinal eccentricity, stimulus size, luminance, contrast, blurring/degradation, and exposure duration. These results are discussed in light of a model of hemispheric lateralization based on asymmetries in the processing of visual spatial frequency.

Temporal integration of form as a function of subject handedness and retinal locus of presentation

Two experiments are reported examining differences in perceptual processing as a function of subject handedness. Experiment 1 compared performance in the left vs right visual fields of right- vs left-handed subjects. Only right-handed subjects exhibited an interaction of visual field with spatial frequency (as mediated by interflash interval), suggesting that left-handers are not differentially lateralized for high vs low spatial frequency processing. Experiment 2 examined foveal performance in left-handers vs right-handers with or without familial sinistrality. Subjects with personal or familial sinistrality exhibited superior performance when the processing of low frequencies was required, suggesting that sinistrality may confer an advantage in the processing of lower spatial frequencies.

Hemispheric differences for visual evoked potentials from checkerboard stimuli

Visual evoked potentials (VEPs) were elicited in right-handed male subjects with an alternating checkerboard pattern stimulus presented to either the left or right visual half-field. The sizes of the individual checks in different conditions were 0.25, 0.5, 2.0, or 4.0 cycles/degree of visual angle. The amplitude of the P100 VEP decreased while peak latency increased as check size decreased across both visual field conditions. Left hemisphere responses demonstrated significantly larger P100 amplitudes compared to the right hemisphere responses, although the interaction between hemisphere and stimulus size was not significant. No hemispheric effects of P100 latency were observed. The results suggest that the left hemisphere is engaged more than the right hemisphere for the sensory analysis of visual stimuli composed of straight edges over a wide range of spatial frequencies.

Lateralized recognition of incomplete figures in a prolonged display controlled by eye movements

A left field superiority is typically reported for processing a variety of simple and complex non-verbal and patterned visual stimuli, including pictures, though stimulus clarity, degradation and exposure duration may be a significant determinant. Clinical studies indicate deficits in the ability to recognize incomplete figures with right hemisphere damage. However when normal subjects attempted to recognize 80 series of progressively-less-incomplete common objects (each series graded in 10 steps) presented for prolonged inspection to one or other visual field via a display driven by an infrared eyemovement transducer, either field (hemisphere) proved to be equally competent. We review evidence to suggest that such "ecologically-more-valid" techniques may not in fact be intrinsically able to tap minor hemisphere function.