Psychology

Optic ataxia and apraxia are common disorders which have some differences and share some similarities. This paper will seek to address the similarities and the differences that the two exhibit in terms of anatomy and their behavior or characteristics.
 
Optic ataxia manifests itself when one has impairment when it comes to visual control of the direction of arm reaching to a visual target.  The impairment in visual control is also accompanied by a defective orientation of the hand as well as the formation of grip. The disorder is also linked to the lesions which are normally present in the superior parietal lobule (SPL) which has effects on the coordination between the eye and the hand. The lesions in the parietal lobe are known to alter the accurate shaping of the hand in accordance to the configuration of the object (Clark, et al, 1994). At this point, it should be understood that the SPL is normally the main source of visual input to the frontal cortex and is normally key to the visual control of movement. Research has actually shown that optical ataxia come as a result of a breakdown between the directional eye and hand information within the global tuning fields of parietal neurons (Walsh, Rushworth, 1998). Basically, optic ataxia can be understood to be the lack of proprioceptive control of movement which is normally characterized by a disorder with the hand reaching movements.

Optic ataxia can also be understood as a neurological symptom which is generally associated with the dysfunction of both the parietal and the frontal lobe. For instance, parietal patients have some defects when it comes to conferring to the hand orientation. This is mainly due to the fact that the patients lack the oriented slot (Milner, Jakobson, Carey, 1991). Visual information processing models also show that optical ataxia is a deficit of the dorsal pathway which normally connects the pre-striate areas to the back side of the parietal lobe.

The disorder is also known to not only impair the visually guide arm reaching because it also affects the visual motor behaviors such as prehension. Also, optic ataxia has close association with the parietal cortex which normally controls the eye and hand movements. The parietal cortex is normally divided into two regions which are concerned with sensation, perception and the integration of the sensory input. The region that is much concerned with the integration of sensory input is of interest in the study about optic ataxia (Walsh, Rushworth, 1998). Optic ataxia is known to occur as a result of damage to the neo-cortex leading to the inability of one to conduct some meaningful movements.

Optic ataxia has a number of symptoms which are distinct from those of apraxia. First, there is the alteration of the kinematics of reach. The kinematics is normally altered in a manner that there is reduction in velocity and the deceleration phase takes sometime to complete. The performance of the patient is also severely affected since the vision of the both the hand and the target are obstructed. Optic ataxia has a subtype called the non-foveal ataxia (Clark, et al, 1994). Patients with the non foveal ataxia can successfully reach to objects which are focused on the foveal but they have the inability to reach to objects situated in the tangential field of vision.

Apraxia
On the other hand, there is apraxia which is normally a neurological syndrome. It reflects dysfunction of the motor system at the cortical level. It is characterized by the inability to execute some purposeful movements despite the fact that one may be willing to perform the movements (Tunik, Fray, Grafton, 2005). Apraxia differs from optic ataxia since it is normally caused by lesions which present themselves in the left hemisphere of the brain which is more language dominant.

Apraxia also differs from the optic ataxia since it is more dominant in children who are learning to acquire their mother tongue. Apraxia patients have the tendency of having a repetition in terms of speech sound repertoire meaning that such individuals will be having limited speech sounds (Leiguarda, 2000). Also, it has the characteristic that, individuals with the condition normally have some level of inconsistency in speech. Research has also shown that apraxia patients normally have problems while accessing vocabularies and they have a limitation in terms of the number of words that they can understand.

Apraxia is distinct from optic ataxia since it is normally a problem with the movement of body parts such as the jaws, limbs and the tongue while the later is normally a problem with grip configuration in accordance to the object that one may wish to hold (Rushworth, Ellison, Walsh, 2001).

Other characteristics that are not present in optic ataxia but are present in apraxia include difficulties especially when one is imitating a speech and some difficulties when saying longer words or phrases. Individuals with apraxia have difficulties in understanding and they always sound choppy or pay much emphasis on the wrong syllables or words (Milner, Jakobson, Carey, 1991). Moreover, apraxia has some other characteristics which are distinct from those of the optic ataxia. For instance, the condition often leads to delayed language development and confusion when recalling words or past instructions. Lack of motor coordination and the inability to read or spell are also features of this disorder (Rushworth, Ellison, Walsh, 2001). There is also the problem with hyper sensitivity and hyposensitivity which results to the failure to identify an object that may be in the mouth.

Apraxia and optic ataxia also differs in the types. For instance, there is the acquired apraxia which affects anyone regardless of their age. This type of apraxia is normally prevalent in adults and it damages the part of the brain which is concerned with speech. Then there is the developmental apraxia (Leiguarda, 2000). This is normally present in birth and is more prevalent in boys than in girls. Common characteristic with this form of disorder is that a child follows the typical path of developing speech but he or she does this slowly.

The two also differ in the fact that, the optic ataxia patients cannot do most of the things independently while for those with apraxia can go on with their day to day operations with minimal or no difficulties except for the fact that their language may not have fully developed. They also differ in the way that one can intervene incase one has a patient of either of the disorders. For instance, the use of sign language is normally a way of intervening especially when an individual has the speech apraxia (Tunik, Frey, Grafton, 2005). Though it can be frustrating, it is normally practical since it involves the use of an augmentative and alternative communication system.

Similarities
Both optic ataxia and apraxia show some similarities. In that, they are both acquiredhereditary and they can develop as a result of other external factors. For instance, sensory ataxia is caused by the loss of sensitivity to joint and the positioning of body parts. This arises when there is dysfunction in the dorsal columns of the spinal cord. Focal lesions in the central nervous system are known to be the major case of optical ataxia. In addition, lack of vitamin B12    is known to be the cause of both the cerebellum and the sensory ataxia. Optic ataxia is also known to be hereditary (Clark, et al, 1994). Hereditary disorders normally result to the degeneration of the cerebellum. Similarly, a child born by parent with this disorder has high probability that he or she will have the same disorder.

The two disorders are normally treated by use of therapies which has so far been found to be effective. For instance, they are treated through the use of physical therapy which is common to both. Also, occupational therapy andor speech therapy are normally effective in the treatment of apraxia. The two have the characteristic that they mainly originate from the dysfunction of the parietal lobule of the left hemisphere of the brain. They also have the common characteristic that they are concerned with limitation in terms of body movements (Milner, Jakobson, Carey, 1991). Only that, optic ataxia is localized to the eye-hand movement while the apraxia are more localized to the jaw and tongue movement which make language acquisition to be slower.

At this point, it is worth concluding that the two disorders differ in the manner they present themselves. Optic ataxia present itself by lack of coordination between the eye and hand movement which translates to lack of a grip which will assume the shape of the object that one may wish to hold. Apraxia manifests itself through the slow development of speech and inconsistency of the same. Finally, the common characteristics between the two are that they are both neurological disorders which originate from the parietal lobe. It has also been deduced that the two results to impairment in body movements (Tunik, Frey, Grafton, 2005). In addition, it is evident that optic ataxia dose not discriminate against age and sex which apraxia is more prevalent in adults and in males. Finally, it has been shown that an optic ataxia patient is less independent than the apraxia patient since the later can conduct his or her chores with minimal difficulties.