Critically Evaluate The Specificity Of The Fusiform Face Area (FFA) (Essay Sample)

Face Perception
Name
Institution
Face Perception
Introduction
The Fusiform Face Area (FFA) is a particular region located within the fusiform gyrus. Presently, there is a heated debate among researchers regarding the true function of this region (Kanwisher, 2000; Grill-Spector et al., 2004). According to some experts in the field of neuroimaging, the FFA tends to be more active when a person is viewing faces than when looking at other images. For instance, when one is subjected to different stimuli such as objects, letters and houses, this region does not get activated (Halgren et al., 2000; Gauthier et al., 1999). There are also other neuroimaging experts who hold the view that, FFA carries out a domain-general operation, as opposed to being involved specifically in the recognition of faces (Gauthier et al., 1999; Gauthier & Tarr, 2002). This paper will critically evaluate the specificity of the Fusiform Face Area (FFA), citing neuroscientific evidence.
Main arguments
In face perception, the most basic aspect is its detection. To do this, the FFA simply extracts the common features that the face to be detected shares with other faces (Bentin et al., 1996). Since the face of a human being has a simple T-shaped schematic outlook, it can be argued that the FFA succeeds in its detection through a basic template-like process. This T-shaped outlook has the eyes, nose and the mouth (Sergent et al., 1994). Face detection is certainly easier to go about as the FFA just needs to check if these three parts are present in the face it is trying to detect. Identification, on the contrary, is relatively more complex as it requires this part to analyze how the new face being identified differs from others the fact that all faces share these three parts notwithstanding (Kanwisher et al., 1997).
According to Tsao and Livingstone (2008), a FFA which is good in detecting faces does not do well in their identification and vice versa. These researchers also assert that, detection can serve as a domain-specific filter, in which case, it ensures that the valuable resources needed for the recognition of faces are only utilized in the event that the stimulus presented to the subject already meets the threshold as far as being a face is concerned. It is for this domain-specificity that the anatomical separation of face processing is present in primates. Preceding face identification with its detection is also vital for the reason that face detection firstly requires its automatic segmentation (McCarthy et al., 1997). Detection therefore first involves the isolation of the face from the rest of its background, therefore, requiring a process of aligning the face with a certain standard template. Since many algorithms for the recognition of faces must be preceded by its segmentation and alignment, the presence of non-harmonious backgrounds and varying sizes of faces result to their failure (Ishai et al., 1997).
Grill-Spector et al. (2006) carried out an experiment to investigate the specific functions of the Fusiform Face Area. In this particular investigation, these researchers measured the actual correlation between the rate of activity of the FFA as measured via functional magnetic resonance imaging (fMRI) and behavioral responses in tasks involving perception. In cases where the subject was able to detect a face, the rate of activity of the FFA region was found to be significantly higher than for those cases in which no face was detected. Moreover, for those incidences in which the subject was able to identify the exact face, the rate of activity of the FFA was realized to be even higher. As such, these researchers were able to arrive at a conclusion that, FFA is involved in both the detection and identification of faces.
The research carried out by Grill-Spector et al. (2006) was also able to realize that, the FFA is not in any way involved in within-category identification of exemplars of any domain of stimuli. This realization shows that the FFA is not involved in the detection or identification of non-face classes such as houses, letters, guitars, and flowers. These experts also tested the hypothesis that the FFA might be involved in helping individuals discriminate objects sharing the same features. To test this hypothesis, these scholars used subjects who were experienced in the identification of cars. However, when these subjects were required to discriminate between various cars assembled in front of them, no trial-by-trial correlation was noticed between the activity rate of the FFA and success in identification. This result certainly shows that the FFA is not involved in the discrimination objects which share a similar basic configuration. Additionally, this result shows that this region does not participate in within-category discrimination of objects of expertise.
Haxby, J.V. et al. (2001) also carried out an investigation into the specific function of the FFA. In their research, these authors realized that categorical information regarding faces and various objects in the ventral visual route is transmitted by both a strong response to the preferred stimulus and a relatively weaker response to all non-preferred stimuli. According to Kanwisher (2010), the FFA has been consistently found in multiple studies carried out in various labs. Therefore, although the theoretical significance of the specialty of this region can be debated, its existence is irrefutable. Moreover, this researcher asserts that, the FFA has been noticed to lie in the same location in virtually all neurologically intact subjects of study. As such, this part can be regarded as a fundamental part of the basic functional architecture of the brain. Additionally, according to this scholar, the category selectivity of the FFA is not only statistically significant but is also tremendous in the magnitude of its effect. Further, Kanwisher (2010) argues that, the FFA responds to its specific stimuli with a magnitude that is twice as strong as that it offers to its non-preferred stimuli.
Kanwisher (2010) asserts that, the FFA offers a stronger response to the faces presented to the subject than to the objects it views. According to this author, the FFA gives a similar response to a broad spectrum of facial images including photos of familiar as well as unfamiliar faces, faces of cartoons, schematic faces, and faces of cats. Moreover, this region offers a significant response to faces of diverse sizes, viewpoints and locations. When this region is presented with non-face objects, the response triggered is not even half of the magnitude it offers to faces. This researcher also disapproves the opinion held by some scholars that the FFA does not specifically respond to faces but serves the work of discriminating between exemplars of various categories for which the viewer has a significance expertise. Additionally, Kanwisher (2010) is of the view that the exact size of the response given by the FFA is correlated with its degree of success in detecting and identifying the faces presented to the subject. This researcher is also of the opinion that, the FFA is sensitive to a broad spectrum of facial aspects including eyes, mouths and noses.
Kanwisher and Stanley (1999) carried out experiments to investigate whether the human FFA offers a response to humans and animals or to faces alone. In their research, these authors utilized fMRI to obtain measurements for the response of this region to a total of six diverse stimuli. Here, they were able to notice that the FFA offered the strongest response to stimuli containing human faces and human heads. For the human faces, a signal increase of 2.0% from the baseline was registered while for the heads, a rise of 1.7% from the baseline was recorded. When the entire human body was subjected to the test, a rise of 1.5% from the baseline was noted. Other results included 1.3% for the heads of animals, 1.0% for the entire body of the animal, 1.0% for human bodies without the head, 0.7% for inanimate objects, and 0.8% for the bodies of animals with no heads. Certainly, these results indicate that, the FFA tends to be more selective to faces as opposed to bodies.
FFA offers a double response to faces compared to that it gives to various non-face stimuli such as inanimate objects like the hands of human beings (Kanwisher and Stanley, 1999). For face stimuli, front-view faces, Mooney faces, cartoon faces, upside-down greying faces and cat faces, FFA offers a general response (Kanwisher and Stanley, 1999; Tong et al., 1997). This generalized response occurs despite the fact that these diverse faces contain features which are largely different. Owing to this generality and specificity, it can be concluded that the FFA is selectively involved in the perception of faces (Farah et al., 1995).
Studies show that, the FFA offers a more general response to animate as well as human stimuli. The response to these two categories is albeit weak, thereby, showing that the amount of stimuli to non-face stimuli is weak and therefore insufficient to stimulate the FFA strongly (Caramazza and Shelton, 1998; Damasio et al., 1996). Although the FFA does not get a strong drive from non-face stimuli, research indicates that there are various other cortical zones that are specialized in this nature of perception. Moreover, the fact that FFA does offer a nearly equal response to objects and animal headless bodies shows that this region selects the presence of a face as opposed to responding to the animal as a whole (Perani et al., 1995; Warrington and McCarthy, 1983). Chao at al. (1998) however give a different view regarding the response offered to objects and human headless bodies. According to these authors, these two categories receive a different amount of response, with the human bodies with occluded heads getting a greater FFA response. The reasons for this assertion by Chao at al. is however not clear a...