The Temporal lobes are one of the most heterogeneous regions of the Neocortex. Arbitrary in its definitive anatomical loci, this area of the brain does not serve a singular function. As such, it houses the 1o and 2o cortex for audition, the 2o cortex for vision, the 3o cortex for sensibility, and input for the Limbic and Para-Limbic cortex. This is the lobe that is credited with being the seat of human para-Psychological and Psychic abilities! Also it is the right Temporal lobe which is responsible for our Dreams!
(See
Figure E )
The phylogenetically older cortex (three layers) of the Temporal Lobe (known as Archicortex and Paleocortex) includes both the cortex on the medial surface of the Temporal Lobe, which forms the Fusiform gyrus, Para-Hippocampal gyrus, and Uncus; and the Hippocampus and Amygdala which are subcortical.
Unlike other lobes of the brain which are connected to their identical twin solely by way of the Corpus Callosum; it is the Anterior Commissure which functions to connect the anterior portions of the Temporal lobes, along with the Amygdala, and the Paleocortex of the Temporal lobes surrounding the Amygdala.
In the Late 19th Century three major effects of Temporal Lobe damage on behavior were documented: in 1876 Karl Wernicke described language deficits, in 1888 Brown and Schaefer noted disorders of affect and personality, and in 1899 Bekhterev reported memory impairment.
It has been known for a century that damage to the Temporal Lobe was associated with memory loss. The loci of which include the anterior Temporal neocortex (six layers), the Amygdala, the Hippocampus, and the Entorhinal Cortex. This last cortex, which is Brodmann's area 28, is the major source of Hippocampal input and output. Thus damage to the Entorhinal cortex would probably destroy afferents to the Hippocampus and disrupt its function, and Hippocampal damage is consistently associated with significant memory loss.
Amnestic Syndrome
refers to a discrete disorder of memory caused by structural disturbance of the CNS. This appears to involve, usually bilaterally, areas of the diencephalon or medial portion of the Temporal lobes, or both. Patients usually display difficulties with both Short-Term Memory (Anterograde Amnesia) and Long-Term Memory (Retrograde Amnesia).
Cryptomnesia involves the remembering of information without recognition of it as a memory. This suggests that individuals can retrieve recently acquired information from memory without experiencing the information as the recall of something that has been recently learned.
Semantic Memory is a form of memory in Hypnosis in which factual information taught while in Hypnosis is recalled, although the source of the memory is forgotten (ie. the Hypnotic Trance itself)! This learned material can be classified as semantic memory.
Attention
of the mind seems to be directed to only one portion of the brain at a time. In early life, it is the left Temporal lobe which begins to be used to a greater extent, than the right, perhaps due in part to its larger size at birth. The Human Mind tends to utilize the better developed region of the brain, and hence the rate of learning in the cerebral hemisphere that gains the first start increases more rapidly. Unfortunately, the opposite side remains slight. As a result, one side of the brain becomes dominant over the other.
When a sensory stimulus is received, several processes must occur to allow the motor system to act on that information.
First - Perception
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A stimulus must be identified and a «Percept» must be formed, which requires that information about a given stimulus be integrated from the different senses, especially vision, audition, and somesthesis. This integrative process is a primary function of the tertiary areas of the Parietal lobes.
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Second - Identification
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Once we have formed a percept of a stimulus, it needs to be indentfied and probably categorized or classified with respect to its function. The processes of identification and classification are probably carried out by the Temporal association cortex, including especially the superior Temporal sulcus. The cortex in the Sulcus is polymodal, receiving input from all sensory modalities; additionally, it receives input from Brodmann's area 7. The direct sensory inputs provide more fine details about a stimulus, whereas Brodmann's area 7 provides the basic percept to bulid on, including the general shape of objects.
Third - Storage
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This information is then stored for future use or for comparing it with material stored previously. Storage requires two components. First, there must be a mechanism that functions to store and to retreive information; this mechanism appears to be within the Temporal lobes, especially the Hippocampus. Second, there must be a mechanism for the actual storage of information -- yet to be deliniated!
The Fourth Step,
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of sensory - input analysis is assigning connotative or affective properties to stimuli - that is, associating them with motivational or emotional significance. This is a crucial function for learning because stimuli become associated with their positive, negative, or neutral consequences, and the resultant behavior is modified accordingly. In the absence of such a system, all stimuli would be treated as equivalent, and there would be a loss of affective response to them. Associating affective properties with particular stimuli is also a function the the Temporal lobes, especially the medial Temporal cortex and the Amygdala. Because of this function, the medial Temporal cortex has been called the association cortex of the Limbic System. It is also likely that the multimodal cortex of the Temporal cortex is also involved in associating affect with stimuli.
Visual or auditory input, leaving the visual and auditory association regions, proceeds to various regions of the medial Temporal lobes. The medial Temporal cortex then projects primarily to the Amygdala and Hippocampus, which are relatively specialized for their affect and memory functions, respectively.
Associated with the dominant Temporal lobe and Angular Gyrus is dominance of certain portions of the somatic sensory and also the motor cortex (controlling voluntary motor functions).
As an example, the premotor speech area (Broca's Area), which is located far laterally in the intermediate Frontal lobe, is almost always dominant on the left side of the brain as well. This speech area causes the formation of words by exciting simultaneously the neurons which innervate the laryngeal muscles, the respirator muscles, and the muscles of the mouth. The motor areas responsible for controlling the hands are dominant on the left side of the brain as well, thus causing right-handedness in almost 90% of humankind!
The sensory area of the Dominant left hemisphere responsible for the interpretation of language is referred to as Wernicke's Area, and is closely associated with both the Primary Hearing Area and the Auditory Association Areas of the Temporal lobe. This very close anatomical relationship probably results from the fact that the first introduction of spoken language is by way of hearing. Later in life, when visual perception of language through the medium of reading develops, the visual information is then presumably channeled into the already developed language regions of the dominant Temporal lobe.
(See
Language )
The right hemispheric equivalent of
Wernicke's Area in the
right Temporal Lobe and
Angular Gyrus is important in the production of contextual items associated with words, in understanding and interpreting music, nonverbal visual experiences (patterns), and spacial relationships between the self and the environment.
Specific to the right Temporal lobe are the perceptions of certain characteristics of music (in the untrained ear), namely pitch discrimination, loudness, rhythm, time, timbre, and tonal memory.
The right Temporal lobe has a special function in extracting pitch from sound, regardless of whether the sound is speech or music. There are however, a variety of other musical aspects that may be specially processed in the right Temporal lobe such as music scales, chords, and progressions, all of which are constructed from single musical notes.
Because verbal skills are the most clearly lateralized function of the brain, verbal access theories of consciousness have led to questions about the relationship between hemispheric function and consciousness.