A Research Proposal:

Visual agnosia is a neurological disorder distinguished by the inability to recognize familiar objects. Most cases of visual agnosia are brought about through cerebral vascular accidents or traumatic brain injury, typically inhibiting sufficient amounts of oxygen from reaching vital body tissues (Farah, 1990). There are a vast array of impaired abilities and deficits associated with individuals diagnosed with visual agnosia. These impairments vary considerably from individual to individual (Farah, 1999). Some patients cannot recognize pictures of things such as trees and birds, despite being able to describe such objects or recognize them through other senses such as sound and touch. Other patients demonstrate an inability to recognize faces of friends and family members (Farah, 1990). Furthermore, some agnosic individuals cannot copy familiar objects in simple drawings. The functional impairments experienced as a result of visual agnosia are detrimental to both the diagnosed individual and all those who interact with the individual.

Unfortunately, object recognition disorders such as agnosia comprise a neglected field of study, and the existing theories to explain this phenomenon are often vague and problematic (Farah, Monheit, & Wallace, 1991). Visual agnosia is a very rare syndrome and there is only a small number of cases available to study. This research obstacle is further compounded by the variance of impairments in visual agnosics (Vecera & Gilds 1998). In an attempt to group similar cases of visual agnosia for more sufficient study, two separate categories have emerged. Apperceptive agnosia is typically characterized by an inability to recognize familiar objects caused by damage to early perceptual processes and associative agnosia is typically characterized by an inability to recognize familiar objects despite having no damage to early perceptual processes (Vecera & Gilds 1998). However, the different fields of study and various researchers involved in studying visual agnosia often have discrepancies in defining these categories.

The most recent explanation for the visual impairments experienced by visual agnosics is the peppery mask account. It is theorized that patients with visual agnosia have a presence of random visual noise as a result of obstructing air bubbles circulating in the blood or from blood clots present in an intact blood vessel (Farah et al. 1991). Because of obstruction, random areas of dimmed vision are scattered throughout the visual field in varying size and severity; thus the visual agnosic sees the world through a peppered mask that degrades their visual processing. In an experiment by Vecera & Gilds (1998), researchers covered different displays with a peppery mask to simulate the peppery mask condition in subjects with normal vision (Farah 1999). Normal subjects were expected to simulate the behavior of a visual agnosic patient when looking through the manipulated mask. However, the manipulation of a peppery mask did not exhibit different patterns of behavior from the patterns of behavior measured from unmasked displays (Vecera & Gilds, 1998). While the peppery mask account explains the degraded low-level visual processing, the theory offers no explanation for the various grouping disorders that tend to appear in visual agnosics.

In an effort to seek understanding and explanation of perceptual grouping disorders researchers formulated the grouping-deficit account. This account hypothesizes that patients with visual agnosia have impairments in preattentive perceptual grouping process (Vecera & Gilds 1998). Such impairments would include difficulty in organizing segments of information into the totality of the information it represents. The main limitation imposed on the grouping-deficit account is that little data exists from patients that examines lower-level grouping processes (Farah 1999). An experiment was conducted to explore the grouping-deficit account. Vecera & Gilds (1998) removed nonaccidental properties from displayed objects, such as parallelism and cotermination, and various aids used to organize or group the visual field. When these properties were removed object recognition and grouping was difficult in normal subjects, if not impossible (Vecera & Gilds 1998).

Currently, researchers are taking new approaches in determining which account of visual agnosia best explains the syndrome. Through experimentation, researchers have been attempting to simulate visual agnosia in subjects with normal vision in order to move beyond individual case studies with agnosia patients. Given the vast differences of impairments between patients with visual agnosia, the lack of clarity in defining categories of visual agnosia, and the failure to formulate a proficient explanation of the cognitive mechanisms behind the hidden perceptual processes that are involved in the syndrome of visual agnosia, it can be concluded that further research is desperately needed. Nevertheless, experiments such as the peppery mask experiments and the grouping-deficit account yield significant pieces of a puzzle that show encouraging signs of fitting together to enhance our understanding and advancement of knowledge surrounding object recognition disorders.

Further compounding the difficulty of defining and understanding agnosia is the proposal of similar impairments present in patients with the same hemisphere of the brain damaged (Humphreys, 1999). Agnosia has been diagnosed in patients with varying types of brain damage. Cases have been noted after both unilateral and bilateral damage to both right and left hemispheres of the brain (Humphreys, 1999). According to Humphreys (1999), left hemisphere patients are typically marked by the inability to copy objects in simple drawings presented in most forms of presentation. Additionally, right hemisphere patients are better are copying objects from real objects presentations when they are allowed to interact with objects and use the senses of touch. Patients with right hemisphere lesions are typically marked by an ability to better recognize and label objects when grouping cues such as color are present while left hemisphere patients are typically can label objects with and without color present. However, left hemisphere patients faced with labeling tasks generally show the same labeling ability with or without color cues (Humphreys, 1999).

The proposed research is intended to bring together a large group of individuals diagnosed with visual agnosia. By focusing research on a large group of agnosia patients instead of using individual case studies or attempting to simulate agnosia in normal subjects, the impairments and deficits can be further explored. There is a need for clear definitions and classifications of visual agnosia in order to advance current research on agnosics. It is proposed that a better understanding and definition of classifications of agnosia can be achieved by conducting object recognition research on a group of agnosic individuals with right hemisphere damage and a group of individuals with left hemisphere damage. Differences between right and left hemisphere patients can be determined and similarities across all visual agnosics can be explored as well. It is hypothesized that different presentation forms of familiar objects will influence the ability to recognize objects and the ability to copy them in drawings with a significant interaction among individuals with right and left hemisphere damage.

Participants

Participants will be individuals diagnosed with visual agnosia randomly selected from a compilation of visual agnosia patients in the United States. A total of 20 individuals will be randomly selected from all visual agnosia patients who respond to an invitation to participate. The total of 20 individuals will include 10 individuals marked by a left hemisphere lesion and 10 individuals marked by a right hemisphere lesion.

Materials

A university laboratory will be used to conduct experiments. Twenty familiar objects will be selected from the objects used in research conducted by Stone, Buckley, & Moger (2000) will be collected. For a list of objects selected see table 1.8. Real objects will serve as color 3D presentations. Each object will be processed into a colorless ceramic mold to serve as colorless 3D presentations. Furthermore, each object will be photographed on both color and black-and-white film, and developed into 10x10 photos to serve as color and colorless 2D presentations. Each participant will be provided with a drawing pad, pencil, and eraser to perform object copying tasks. Additionally, experimenters will be provided with scoring sheets to rank the level of object identification and the level of copying ability. Each participant will also be provided with a set of experiment instructions, and a copy of the consent form and debriefing form.

Dog	Train	Iron
Dinosaur	Toothbrush	Bicycle
Cow	Cup	Shoe
House	Chair	Tennis Raquet
Boat	Stapler	Key
Car	Flower	Bird
Pig	Saftey Pin	Bird

Design

The experiment proposed is a 4 x 2 within subjects design with the variables Type of Presentation (real object, ceramic mold, color photo, black and white photo) and Type of Brain Lesion (right, left). The two dependent variables proposed are the given ranks on the prescribed scale of one to three given for the object labeling task and the rank on the prescribed scale of one to three given for the object copying task. It is hypothesized that different presentations of familiar objects will influence the ability to recognize objects and the ability to copy them in drawings with a significant interaction among individuals with right and left hemisphere damage. Right hemisphere patients are hypothesized to perform poorly on object labeling tasks when color cues are not present while left hemisphere patients will show no significant difference in labeling tasks with or without color cues. Furthermore, left hemisphere patients will perform poorly on object copying tasks in all forms of presentation while right hemisphere patients will perform better at copying tasks when color cues are present.

Procedures

Participants will enter the university laboratory and they will be given a copy of the consent form and experiment instructions, as well as a drawing pad, pencil, and eraser. The experimenter will read and explain both the consent form and instructions orally to participants and have them marked their signature on the consent form.

In order to prevent the systematic influence of top-down processing on labeling and copying tasks, half of the participants are to be randomly assigned to label objects first and copy objects second, while the other half of participants are to be randomly assigned to copy objects first and label objects second. Participants with right hemisphere lesion (R1 through R10) and participants with left hemisphere lesions (L1 through L10) will be randomly assigned to two groups. Group A will be asked to label the object and then draw and group B will be asked to draw the object and then label in order to prevent the systematic effect of top down processing.

Participants may be marked by learning and fatigue effects as a result of being presented the same object in four different levels of presentation. To counterbalance this effect, the 10 left hemisphere lesion patients and 10 right hemisphere patients are to be randomly assigned to one of five prescribed orders of presentation levels. Participants L1 & L6 and R1& R6 will be presented random familiar objects in presentation form order of real object, ceramic mold, color photo, and black and white photo. Ps L2 & L7 and R2 & R7 will be presented random familiar objects in presentation form order of ceramic mold, color photo, black and white photo, and real object. Ps L3 & L8 and R3 & R8 will be presented random familiar objects in presentations form order of color photo, black and white photo, real object, and ceramic mold. Ps L4 & L9 and R4 & R9 will be presented random familiar objects in presentation form order of black and white photo, real object, ceramic mold, and color photo. Finally, Ps L5 & L10 and R5 & R10 will be presented random familiar objects in presentation form order of color photo, real object, black and white photo, and ceramic mold.

Each time a participant is presented with a familiar object in any form of presentation they will be allowed to interact with the object through touch. According to Zemel, Behrmann, Mozer & Bavelier (2002), agnosia patients who are allowed to physically attend to objects will exhibit a stronger ability to recognize objects. After Group A is presented with a familiar object, they will first be asked to label the object. Experimenters will rank the subjects ability to label an object on a one to three scale with a rank of one indicating a completely incorrect label, a rank of two indicating a correct category identified, and a rank of three indicating a correct label. Group A will then be asked to draw the object from its form of presentation and experimenters will then rank their ability to draw on a one to three scale. A rank of one will indicate a completely incomparable drawing, a rank of two will indicate a partially comparable drawing, and a rank of three will indicate a comparable drawing.

When members of Group B are presented with a familiar object they will first be asked to draw the object from its form of representation and then label the object and experimenters will then rank them on the appropriate one to three scale.

After participants have been presented all presentations of the twenty familiar objects the experimenter will read a debriefing form to participants and answer any questions regarding the general nature of the experiment before being released.

In an experiment conducted by Zemel et al. (2002), ranking scores were generated from subjects in object labeling and copying tasks. The data to be collected in this experiment will be the labeling task and copying task ranking scores similar to the ranking scales used by Zemel et al. (2002). Labeling task scores are to be submitted to a within subjects 4x2 factorial ANOVA. It is hypothesized that a significant interaction will be revealed. It is proposed that participants with left hemisphere lesions will perform better than participants with right hemisphere lesions when object presentations are without color (ceramic molds and black and white photos) while participants with right hemisphere lesions will perform better when objects presentations include color (real objects and color photos).

According to Humphreys (1999), patients with right hemisphere lesions are typically marked by an ability to better recognize and label objects when grouping cues such as color are present. Left hemisphere patients are typically show no differences in labeling ability between objects with color cues and objects without color cues.

Secondly, copying task rankings are to be submitted to a separate within subjects 4x2 factorial ANOVA. It is hypothesized that results of this analysis will reveal a significant interaction with right hemisphere lesion participants performing better than left hemisphere lesion participants in all forms of object presentation. Furthermore, the analysis will reveal right hemisphere lesion participants performing significantly better at copying from the presentation of real objects verses the other presentation types (Humphreys, 1999).

According to Humphreys (1999), left hemisphere patients are typically marked by the inability to copy objects in simple drawings presented in most forms of presentation. Furthermore, right hemisphere patients are better are copying objects from real objects presentations when they are allowed to interact with objects and use the senses of touch.

The results will support the hypothesis that different presentations of familiar objects will influence the ability to recognize objects and the ability to copy them in drawings with a significant interaction among individuals with right and left hemisphere damage.

Agnosia patients with right hemisphere lesions will perform better at labeling familiar objects when color is present. It is suggested by Humphreys (1999) that patients with right hemisphere lesions perform poorer at object recognition as they become increasingly removed from objects (from 3-D to 2-D and moving from color presentations to colorless presentations). Furthermore, agnosics with left hemisphere lesions will exhibit an inability to copy objects from any form of presentation (Vecera & Gilds 1998). Additionally, right hemisphere agnosics will perform better at copying familiar objects when they are allowed to interact with real objects (Zemel et al. 2002). Right hemisphere patients generally perform better at copying objects from real object presentations (Vecera & Gilds 1998).

The proposed experiment is intended to expand on the current knowledge of the different various impairments present between right and left hemisphere lesion agnosics. An experiment with a large group of individuals with visual agnosia would help to provide clear definitions of subtypes of visual agnosia. A large group exhibiting similar impairments would be better equipped to generalize subtype definitions to all individuals with agnosia as opposed to the current limited research on individual case studies.

Furthermore, current research intended to focus on the ability to learn to recognize objects is also limited by the lack of research on a large group of individuals with visual agnosia (Bischof, 2002). While researchers have been able to work with an individual case studies in an effort to help them learn to recognize objects, not enough research on a large group of individuals has been done and therefore the learning techniques are not able to be generalized to all individuals with visual agnosia (Bishof, 2002). By determining specific impairments characteristic of right and left hemisphere patients, research can begin to focus on overcoming these specific obstacles. Additionally, pioneering work on the role of object appearance and its influence on object recognition is lacking in the ability to generalize a sample of agnosia patients to the population of all agnosia patients (Appearance Based Approaches to Object Recognition).

In conclusion, some researchers share the viewpoint that research in the area of visual agnosia and object recognition will not only be applied to patients diagnosed with visual agnosia, but also advance the overall understanding of visual agnosia (Visual Object Recognition). Given the vast differences of impairments between patients with visual agnosia, the lack of clarity in defining categories of visual agnosia, and the failure to formulate a proficient explanation of the cognitive mechanisms behind the hidden perceptual processes that are involved in the syndrome of visual agnosia; it can be concluded that the proposed research is a type of research that would be a necessity to understanding visual agnosia.

Bischof, W.F. (2002) Learning to Recognize Objects. Spatial Vision. 13 (2-3), 297-304.

Farah, M.J. Visual Agnosia: Disorders of Object Recognition and What They Tell Us About Normal Vision. The Mit Press: Massachusettes, 1990. 155p.

Farah, M.J, Monheit, M.A. & Wallace, M.A. (1991) Unconscious Perception of Extinguished Visual Stimuli: Reassessing the Evidence. Neuropsychologia, 29, 949-958.

Farah, M.J. Relations Among the Agnosias: Case Studies in the Neuropsychology of Vision. The Psychology Press: UK, 1999.

Humphreys, G.W. Case Studies in the Neuropsychology of Vision. The Psychology Press: UK, 1999.

Stone, J.V., Buckley, D., & Moger, F.A. (2000) Determinants of Objects Recognition. Vision Research. 40 (20), 2723-2736.

Vecera, S.P. & Gilds, K.S. (1998) What Processing is Impaired in Appreceptive Agnosia: Evidence from Normal Subjects. Journal of Cognitive Neuroscience. 10 (5), 568.

Zemel, R.S., Behrmann, M., Mozer, M.C. & Bavelier, D. (2002) Experience Dependent Perceptual Grouping and Object-Based Attention. Journal of Experimental Psychology: Human Perception & Performance. 28 (1), 202-217.

Appearance Based Approaches to Object Recognition (n.d.) Retrieved March 3, 2002, from www.prip.tuwien.ac.at/Research/ObjectRecognition/

Visual Object Recognition (n.d) Retrieved March 3, 2002, from http://cognet.mit.edu/MITECS/Entry/Farah2