Another example of a dependent relationship is sensory information and memory. There are two main pathways where visual information is sent. The dorsal stream reaches the posterior parietal cortex so one can receive information on where things are. The ventral stream takes messages to the inferotemporal cortex so a person realizes what things are. Memory tests on monkeys have shown that when remembering a previously presented pair of visual images, there is first action in the rhinal neurons and then the inferotemporal cortex (Pinel, 2003, p.287). This goes along with the idea that the rhinal cortex is a key factor in one’s ability to recognize what things are (Pinel, 2003, p.284). The rhinal cortex is involved in the process of recognizing objects because it is part of the medial temporal lobe, which is shown to affect explicit memories (Pinel, 2003, p.280-289). Therefore, the sensory hierarchy is important in processing stimuli. Visual stimuli are decoded by the dorsal and ventral streams. The ventral stream’s main destination, the inferotemporal cortex, is related to rhinal neurons. These are then associated with the medial temporal lobe, which also involves the hippocampus and amygdala (Pinel, 2003, p.280). This example is one of many that explain the complexities of the networking systems in the human brain.
Since various functions of the brain rely on other functions, it cannot be distinguished as to which is higher order and which is lower order because they depend upon each other. A function cannot be classified as “higher-order” if it is relying on another function to perform its task effectively. This is because the function in question would not be what it is without assistance from other areas performing related tasks. For example, the two visual pathways described above were the dorsal and ventral pathways. Each had two distinct, but related tasks (Pinel, 2003, p. 169). An example of the problem with classifying different functions as “higher-order” or “lower-order” is presented. Pinel (2003, p.170) describes a patient that had damage to her ventral prestriate cortex, which is part of the pathway for the ventral stream, and thus, was unable to recognize the difference between toy blocks of different shapes and sizes. However, she could accurately reach and pick them up without any awkward fumbling. Moreover, the next patient described had damage to her occipitoparietal region, which is in the dorsal pathway. She was unable to accurately reach and grab hold of objects even though she could use her fingers and show accurate measurements of the objects (Pinel, 2003, p.170). These patients both had damage to a part of the visual cortex pathways, but neither of the affected regions was at the end of the pathways, where it would be considered that the “higher order” function of the pathway would be. Therefore, any point in the pathway is essential for proper functioning.
In addition, the two pathways and functions are similar in purpose. If one is to decide on a “higher order” function, the importance of the task should be considered. Both pathways and functions along the way have a mutual relationship, but neither the posterior parietal cortex (the dorsal stream) nor the inferotemporal cortex (the ventral stream) could be classified as “higher order”. To do this, one would have to decide if it is more important to know what objects are or know where they are. Whatever one chooses, it is safe to assume that there will be others disagreeing or some that think it is an impossible question and both are equally important.
Finally, it does not seem plausible to divide “higher-order” and “lower-order” functions in the human brain because there are still many mysteries. The most effective method for examining functions of the brain is studying people with brain damage. Another common method is to test animals, but that is not always the most reliable method because it only has a certain amount of reliability since it is not tested on humans. Both of these tests have their problems. Obviously, some conditions or damages to the brain are rare. Few people have the specific condition and only so much research can be conducted. This creates a challenging opponent for researchers. It is a basis of psychological research that there is a representative sample. Clearly, only so much can be discovered and theorized when there is only a small population to test. Animals are presumably the next best thing. The obvious problem with this is that they are not exactly like humans. With these problems and others, it is a valid statement to say that the human mind still contains many undiscovered or unresolved mysteries.
One current mystery to look at is Anosognosia. People with the disorder perform a function with the part of their body that is paralyzed. They obviously fail the task, but insist they performed it (Horgan, 1996). Some cannot even recognize when others do not perform the task. Research has suggested that there is a certain neural region in the brain, which stores information about the body. Therefore, if this part becomes damaged, then it is conceivable that new information cannot be stored and thus, the individual cannot recognize a paralyzed limb (Horgan, 1996). Perhaps this area is also involved with the perception of others. Horgan (1996) states that, “Anosognosia has long fascinated cognitive scientists because it suggests that perception and self-awareness may be distinct functions carried out by separate parts of the brain,” It appears that research is headed in the right direction, but much more research needs to be done concerining this important condition. It is definitely an interesting condition that could lead to major revelations about the inner workings of the human brain.
Another mystery or unsolved issue often surrounds a specific system or structure of the human brain. One example is the hippocampus. It is clearly stated in many publications that it is unknown as to what exact features of memory it is involved in. Bower (2003) explains that it is typically referred to as a “hub for memory”. However, his article investigated a study that involved participants with hippocampal damage and the results concluded that they could remember experiences from before their injury, but for certain periods of time they were unable to recall specific, well-known facts. Other sources (Bower, 2003; Manns, Hopkins, & Squire, 2003; Suzuki, 2003) have also concluded that the hippocampus may coordinate the recollection of episodic and semantic memory. It is suggested that it assists the medial temporal lobe cortex in memory that relates to the recognition of objects (Worman & O’Reilly, 2003). Pinel (2003, p.279) explains that the hippocampus relays memories to their appropriate places and retains them. He also includes information that describes the hippocampus as being essential to spatial memory, reference memory, and working memory (Pinel, 2003, p.286). Since information on the exact functions of the hippocampus are still disputed (Bower, 2003; Manns, Hopkins, & Squire, 2003; Suzuki, 2003; Worman & O’Reilly, 2003) it does not seem accurate to give it a label of “higher-order” or “lower-order” functioning.
In conclusion, structures and systems of the human brain are not and cannot be clearly divided in terms of whether they are responsible for “higher-order” (complex) or “lower-order” (simple) psychological capacities and functions. The sensory hierarchy, which contains separate levels that are all equally responsible for interpreting a different part of the sensory stimuli until it has been decoded finally by the association cortex, has an important relationship (Pinel, 2003, p.162). These relationships like many others in the brain are essential and vital to the existence of many other specific functions. Since so many different capacities and functions and/or systems of the brain depend on other functions, specific parts of the brain cannot be classified in different orders (e.g. “higher-order” or “lower-order”). To do this would assume one function as more important to human functioning in general. However, if this function is vital to human functioning and classified as “higher-order”, then it would only make sense to classify every other system that has contact with it as “higher-order”. This creates a problem because it appears, although unknown by anyone, that virtually every aspect of the brain is connected to almost every other aspect of the brain in some way. Moreover, the only logical way a function could be classified as “higher-order” is if it was exclusively independent of any other functions or systems in the human brain. Since there is not a definitive answer of every relationship that exists in the human mind, then it is still considered a great mystery to many. Science is continually discovering new dilemmas that the mind is creating. Disorders such as Anosognosia, as discussed previously, is a relatively new condition with a strong need for further research. Other concerns for psychology are more widely known diseases such as Parkinson’s and Alzheimer’s disease. These issues deal with the brain and evidently represent the mysteries that the great scientists of today and tomorrow must discover. The human mind is a complex system. It is one that could not be re-created by any man. The latest and most fascinating discoveries on the human brain are still new and it does not seem logical to classify systems that are not fully understood.
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