Perception of Face Parts - Case Study Example

Perception of Face Parts and Face Configurations: An fMRI Study Face recognition is a unique and essential ability possessed by primates and has beenfound to be one of the most highly developed visual perception skill amongst humans (Haxby, Hoffman, & Gobbini, 2000). Humans are a unique species in that they are endowed with the ability to identify and distinguish between multitudes of different faces, an attribute which requires a complex interplay between multiple, bilateral, specialized brain regions. The article, ‘Perception of Face Parts and Face Configurations: An fMRI Study,’ by Liu et al. (2010), discusses the different aspects of facial recognition with particular emphasis on the evidence obtained from fMRI studies on whether the areas of brain specialized to perform facial recognition are responsive to first order aspects of face or not (Liu, Harris, & Kanwisher, 2010). This paper critically analyses this study and points out the various strengths and limitations of this article. The main objective of the study as stated by authors was to ascertain which aspects of the facial features (i.e. facial parts vs. facial configuration) serve as a stimulus in facial perception and recognition (Liu, Harris, & Kanwisher, 2010). They aimed to discern this with the aid of fMRI, which is a relatively novel modality which can be used to map brain functions depending on the amount of blood flow to different regions of the brain (Kim, 2010). Why faces are special? Faces are special in that every face is unique and humans possess the ability of not only perceiving and recognizing faces but also of linking each face to a particular identity (Haxby, Hoffman, & Gobbini, 2000). Face recognition has been considered to be an important survival skill amongst primates, the importance of which can be gauged by the intricate and complex mechanisms and neural process involved in face identification and recognition, the extent of memory and brain capacity dedicated to carry out this function and the predilection of infants to focus on faces since a very early age (Wilson & Keil, 2001). Moreover, in addition to providing an identity to individuals, the recognition of faces and facial features is also important as it facilitates social interactions. Thus, special mechanisms and highly developed visual perceptual skills are required to facilitate the accomplishment of both these important functions, viz. identification and social communication (Haxby, Hoffman, & Gobbini, 2000). As discussed below, these two important components of facial recognition are carried out by different regions of the brain (i.e. the occipital and fusiform areas for identity and the face selective region for social identification) which are highly specialized to exclusively carry out the aforementioned functions. Neuropsychological aspects of face processing: Facial perception is achieved via neural processing and representation in multiple areas of the brain located in both cortices (i.e. there is bilateral representation). The main cortical region involved in facial perception is the occipitotemporal visual extrastriate cortex which has three distinct regions involved in different aspects of facial perfection, viz. the inferior occipital gyrus, the lateral fusiform gyrus, and the superior temporal sulcus (Haxby, Hoffman, & Gobbini, 2000). Studies using the fMRI technique have revealed that the fusiform face area (Kanwisher, McDermott, & Chun, 1997; McCarthy, Puce, Gore, & Allison, 1997) is located in the mid-fusiform gyrus; the occipital face area (Gauthier et al., 2000) is located in the lateral inferior occipital gyri; and the face selective region is located in the superior temporal sulcus posterior (Allison, Puce, & McCarthy, 2000; Hoffman & Haxby, 2000). It has been found that even though all of these structures in the brain are responsible for processing and perception of the face, each are responsible for a different part of the sensory processing. The occipital face area and the fusiform area are responsible for individual identity perception, while the face selective region is more involved in the social information (Calder & Young, 2005; Haxby, Hoffman, & Gobbini, 2000). What this relates to is that the occipital face area and fusiform area may access visual memory as a way of trying to recognize if the face being presented is already stored in memory. The face selective region might be able to perceive the gender, ethnicity, etc. of the individual- social characteristics that help determine the identity of the individual. First Order vs. Second Order Facial Features: Perception is the method by which we as humans take in external sensory stimuli and form our idea or thought patterns regarding the stimuli. The perception and recognition of faces is a process distinct from the recognition of all other objects and is carried out by specialized regions of the brain (Kanwisher, McDermott, & Chun, 1997). Faces are distinguished from general objects by means of utilization of information regarding facial features. Facial features can be broadly classified into two main categories viz. first order and second order features. The first order characteristics of a face include ‘the basic spatial layout of features that is repeated in all faces (two eyes, above a nose, above a mouth)’ (Taubert, Parr, & Murphy-Aagten, 2010). On the other hand, second order features include the orientation or the configuration of the first order features with respect to each other, for example, the distance between the eyes, having a wide chin versus a narrow chin, etc (Tanaka & Sengco, 1997). Critical analysis of the Rationale: Keeping in view the above discussed aspects of facial perception, it can be gauged that this is an area of research which still has several unexplored and underexplored aspects. The introduction and background provided by the authors in their article ‘Perception of Face Parts and Face Configurations: An fMRI Study,’ gives an adequate theoretical framework and appropriately identifies gaps in the existing literature. The authors clearly point put what is known regarding the topic in question and then identify the gaps in the existing literature. As pointed out by the author, since most of the studies carried out in relation to facial perception have focused on second order facial stimuli, there is a paucity of available data regarding first order stimuli and their role in facial perception. Thus, this study was conducted in order to determine the magnitude of response in the three different brain regions involved in face perception, in response to either face parts or face configuration. (Liu, Harris, & Kanwisher, 2010). Critical Analysis of the methodology: The integral part in the methodology from which the information was obtained from this study lies in the functional neuroimaging techniques that were used. The reason that the use of functional neuroimaging techniques are a better choice for this study as compared to structural neuroimaging techniques is that the study was interested in the brain in respect to cognitive functions that were going on, not just the physical structure. Functional MRI of fMRI, as it is commonly known as, is a hemodynamic-based brain imaging technique that measures the amount of blood flow going to certain parts of the brain when certain parts of the brain are engaged in a cognitive task (BOLD-fMRI) (Kim, 2010). The functional MRI utilizes the differences in the concentrations of deoxyhemoglobin in the venous blood as an endogenous contrast medium. Thus, the fMRI differentiates the level of activity between different brain regions based on the metabolic activity of the regions. The greater the metabolic activity going on in a particular area, the greater would be the oxygen utilization, leading to a higher concentration of deoxyhemoglobin, which results in an alteration in the signal intensity on the MRI images (Kim, 2010). The fMRI offers extremely good spatial resolution compared to other neuroimaging techniques (Lorberbaum, J.). One of the downfalls of fMRI is the way in which it is taken. It is done in an enclosed space and can become distorted at the slightest amount of movement. Also, blood movements in the brain due to capillary structures and changes in blood flow could alter the results picked up. In relation to the study, the fMRI is an invaluable technique because of the close proximity of the structures being observed. All three structures in the brain were located in the same lobe of the brain. This technique allows greater input in the area to get more specific. The research also hypothesizes that these structures are connected in that the perception is the result of interactions between each structure. The fMRI would be able to pick up the changes of blood flow and oxygen/deoxygenated blood ratios. Other techniques that could be valuable to supplement the research could be an EEG or electroencephalography. The EEG can be used to pick up the electrochemical signals that are occurring in the brain much faster and with greater sensitivity than the blood flow that is detected by the fMRI (Electroencephalography (EEG)). Both of these techniques can be used together to create a high resolution of the processes going on in the brain. Critical Analysis of the Conclusions: This study concluded that the occipital face area responds to and processes information regarding only the facial parts and not facial configuration while the fusiform face area deals with both processing the facial parts as well as the facial configuration. Moreover, it was also found that the integration of information regarding the two different types of stimuli, i.e. facial parts and facial configuration took place only in the fusiform face area. This shows that the circuit does not function in a linear or circular manner, but as a method of interaction and multiple processing. Some of this evidence was supported by earlier experiments that were conducted. Using these findings and integrating them with the findings from the previous research conducted in this regard, the authors propose a possible hierarchy between these three regions, whereby information regarding facial parts is initially processed by the OFA and is then transmitted to the FFA where it is integrated with information regarding facial configuration in a feed-forward manner (Liu, Harris, & Kanwisher, 2010). Although the results of this study were found to be statistically significant, there are certain shortcomings and limitations of this study. Firstly, the sample size for this study was extremely small, i.e. only 10 participants were recruited. Moreover, these participants were specifically selected for right-handedness and good vision from a population, which led to a significant selection bias. This limits the reliability of the findings and the generalizability of the results. Therefore, the conclusions drawn from this study cannot be applied to the entire population because it was derived from a small, specifically selected population. Another limitation of this research was that the experiment showed that in addition to the facial parts and the configuration of those parts, the contour of the face was also involved in facial recognition. Based on this, further investigation is required to make sure that this process occurs in the same region as the other parts and does not involve input from other parts of the brain. The research was able to point out that there was a connection among each of the three neural structures; however, the specific mode and pathway of the connection could not be determined. There was sufficient integration of the past research with the current research, allowing for conclusions and connections to be drawn among the data and verified. Even though the data supports only a specific population, the findings can be generalized to the whole population once the experiment is performed on a randomly selected population to be sure that there are no confounds that could have occurred in the experiment. Further experimentation is needed in figuring out what part the contour of the face plays in perception and processing of facial stimuli. Also, the mode by which these structures are activated and communicate/transmit information to one another is also important to understand and could be obtained by doing lesion studies on these areas. 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