What is the difference between the processing of visual information and auditory information?

Question

We can read:

The visual cortex is located in the occipital lobe of the brain and is primarily responsible for interpreting and processing visual information received from the eyes. The amount of visual information received and processed by the visual cortex is truly massive. Nearly half of the brain is in some way dedicated to vision—either direct communication pathways from the retina of the eyes to the occipital lobe, or to indirect visual processing and visual skills. The visual cortex is divided into six critical areas depending on the structure and function of the area. These are often referred to as V1, V2, V3, V4, V5, and the inferotemporal cortex. The primary visual cortex (V1) is the first stop for visual information in the occipital lobe.

We can read:

The primary auditory cortex is the first region of cerebral cortex to receive auditory input.

Perception of sound is associated with the left posterior superior temporal gyrus (STG). The superior temporal gyrus contains several important structures of the brain, including Brodmann areas 41 and 42, marking the location of the primary auditory cortex, the cortical region responsible for the sensation of basic characteristics of sound such as pitch and rhythm. We know from research in nonhuman primates that the primary auditory cortex can probably be divided further into functionally differentiable subregions.[36][37][38][39][40][41][42] The neurons of the primary auditory cortex can be considered to have receptive fields covering a range of auditory frequencies and have selective responses to harmonic pitches.[43] Neurons integrating information from the two ears have receptive fields covering a particular region of auditory space.

The primary auditory cortex is surrounded by secondary auditory cortex, and interconnects with it. These secondary areas interconnect with further processing areas in the superior temporal gyrus, in the dorsal bank of the superior temporal sulcus, and in the frontal lobe. In humans, connections of these regions with the middle temporal gyrus are probably important for speech perception. The frontotemporal system underlying auditory perception allows us to distinguish sounds as speech, music, or noise.

On top of that it is known that the structure of the neurons in the cortex is the same where ever you look (though the division of the visual system is structure-based as can be read above). The information processing is just different in both (the neurons have different connection strengths).

How do the two processes, though implemented on the same structure, differ from one another? Is the process of hearing more a serial parallel process due to the serial character of sound? How are the connection strengths between neurons involved? Wat makes sound different from vision?

Answer 1

Visual and auditory senses are processed completely independently, up to a point. Obviously, they rely on different physical quantities (air pressure for sounds, photons for vision), are sensed by different organs (cochlea for sounds, retina for vision). Finally they reach the brain in different areas (mostly, but not exclusively, V1 for vision and A1 for audition). We are pretty sure they are processed completely independently up to this point. Then it becomes less clear.

Psychologically there are known interactions between the visual and auditory senses (the ventriloquist effect or the McGurk effect for examples). Physiologically there are areas that respond to both and demonstrated effects of one modality on the other in most areas, including by the way V1 at least in rodents. Although it is still unclear what these interactions are and whether they exists in all species.

For the rest, these questions are way too broad to be answered without providing a complete lecture on the state of knowledge in the field. But basically because these senses are processed independently at early stages, there is good evidence that they are processed quite differently. But as they obviously interact in the cortex they must be converted into some sort of common framework at some point. This "common framework" is most likely modality-specific (spatial localization, time perception, language etc.) because of the functional specialty of cortical areas.