Nervous system
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
The final lobe of the cerebrum is the temporal lobe which is separated from the frontal and parietal lobes by the lateral sulcus (Sylvian fissure). It consists of the primary auditory cortex, the auditory association area and a number of limbic system structures including the hippocampus (Figure 12.10). The primary auditory cortex receives sound information in terms of pitch, rhythm and volume from the inner ear via the auditory nerve. The auditory association area interprets and translates these noises as speech, music or other familiar/unfamiliar sounds. Memories of sounds heard in the past are also stored in the temporal lobe, and we observed earlier in the chapter that the hippocampus is closely associated with the formation and retrieval of memories. The temporal lobe also seems to play an important role in face and object recognition and speech and language processes (Wernicke’s area is situated where the temporal and parietal lobes meet). Damage to the temporal lobe can result in a condition called agnosia where individuals are unable to recognise common objects, sounds, shapes or smells. The type of agnosia is dependent on which part of temporal lobe (or elsewhere) has been affected. For example, auditory agnosia often occurs following damage to the superior temporal lobe whereas visual agnosia occurs as a result of damage to the middle-inferior temporal lobe or posterior occipital lobe.
Physiology of Hearing
James R. Tysome, Rahul G. Kanegaonkar in Hearing, 2015
The first site of binaural convergence of the cochlear nucleus output is the superior olive complex (SOC). There are three main SOC nuclei: the lateral superior olive (LSO), the medial superior olive (MSO) and the medial nucleus of the trapezoid body (MNTB). The MSO encodes interaural time differences while the LSO encodes interaural level differences. The MNTB is the site of giant synapses from cells in the cochlear nucleus and provides inhibitory input to other nuclei in the SOC. The output of the SOC joins projections from the cochlear nucleus that form the lateral lemniscal tract. This tract terminates in the inferior colliculus. The auditory midbrain consists of the inferior colliculus (IC) and the superior colliculus (SC). Cells in the IC have been found to be spatially selective but no map of auditory space has been found in this nucleus. In contrast, a map of auditory space does exist in the deep layers of the SC and is usually aligned with a visual map of space. It is fair to say that there is no clear idea of the functions of the mammalian auditory cortex when compared with the visual cortex. The primary auditory cortex is tonotopically organised and is bordered by one or more adjacent auditory areas.
Cortical Deafness (Plus Other Central Hearing Disorders)
Alexander R. Toftness in Incredible Consequences of Brain Injury, 2023
What makes cortical deafness so rare is that it requires brain damage to large parts of both sides of the brain (Graham et al., 1980). Specifically, damage to parts of both of the auditory cortices located in the temporal lobes. One fun fact about the way that the brain is wired is that incoming sound wave information from both ears is shared with both auditory cortices. Therefore, a person who has damage to just one auditory cortex will not experience cortical deafness, and may not show significant impairments to hearing at all (Polster & Rose, 1998). Because the auditory cortices are located far away from one another, the typical person who develops cortical deafness first has a stroke in one auditory cortex, and then later has another stroke in the other one (Brody et al., 2013).
Emotional arousal modifies auditory steady state response in the auditory cortex and prefrontal cortex of rats
Published in Stress, 2019
Yuchen Wang, Zijie Li, Zemin Tian, Xuejiao Wang, Yingzhuo Li, Ling Qin
At the lower level of the auditory hierarchy, the primary auditory cortex (A1) is the first station of cortical auditory processing, which plays a key role in the sound representation and auditory perception (Dong, Qin, Liu, Zhang & Sato, 2011; Dong, Qin, Zhao, Zhong & Sato, 2013). The A1 is connected to the mPFC via both direct and indirect anatomical pathways (Van Eden, Lamme, & Uylings, 1992). Previous electrophysiological studies on animals have shown that the mPFC and A1 show similar neuronal processes (Rodgers & DeWeese, 2014) and dynamically establish a functional connection during auditory discrimination processes (Fritz, David, Radtke-Schuller, Yin, & Shamma, 2010). Magnetoencephalographic data from human participants also showed an enhanced feed-forward theta/alpha-band connectivity between auditory-prefrontal networks during auditory mismatch detection (Recasens, Gross, & Uhlhaas, 2018). It has been proposed that the auditory-frontal cortical connection may drive the subject’s behavioral choice in response to different sound stimuli (Concina et al. 2018).
Investigation of the effect of cochlear implantation on tinnitus, and its associated factors
Published in Acta Oto-Laryngologica, 2020
Wen-Hui Hsieh, Wen-Ting Huang, Hung-Ching Lin
Tinnitus, defined as the sensation of sound without an external acoustic stimulation, is one of the most common symptoms in patients with hearing impairments [1]. According to the measurability and audibility of tinnitus, a patient’s condition can be either objective or subjective. The majority of the patients present subjective tinnitus and is known only when reported. In 1970, the edge theory [2] claimed that tinnitus is an inappropriate response due to the reorganization of the tonotopic thalamus because of the reduction in afferent auditory signals in the damaged cochlear area. Twenty-three years later, Jastreboff and Hazell [3] proposed the discordant theory indicating that it is an unexpected signal arising from the depolarization of the inner hair cells owing to the abnormal movement of the basilar membrane and partial collapse of the outer hair cells and tectorial membrane. In the central auditory system, afferent signals are reorganized and transmitted in tandem to the other regions of the brain owing to the abnormality in acoustic signals arriving in the dorsal cochlear nucleus, which maintains the balance of afferent signals, and increasing the possibility of tinnitus [4]. The synchronized spontaneous firing between uncovered neurons and normal neurons could be one of the attributors [5]. Tinnitus can be triggered along the auditory pathway [6]. It is believed to be encoded in neurons within the auditory cortex. The majority of profound sensorineural tinnitus were due to pathology at the cochlea or cochlear nerve level.
Gap detection responses modelled using the Hill equation in adults with well-controlled HIV
Published in International Journal of Audiology, 2023
Christopher E. Niemczak, Christopher Cox, Gevorg Grigoryan, Gayle Springer, Abigail M. Fellows, Peter Torre, Howard J. Hoffman, Jay C. Buckey, Michael W. Plankey
While peripheral mechanisms in the cochlea encode temporal aspects of sound, the auditory cortex also contributes to auditory temporal processing (Eggermont 2000; Rupp et al. 2002). For example, Bertoli, Smurzynski, and Probst (2002) compared psychoacoustic gap detection thresholds with auditory electrophysiological responses evoked by varying gap durations. They found evident mismatch negativity responses when a silent gap within a 1.0-kHz sinusoid was approximately 9 ms as compared with behavioural gap detection thresholds at approximately 6 ms in the same listeners. Additionally, Rupp, Gutschalk et al. (2002) found evidence from neuromagnetic recording of middle latency responses that showed the primary auditory cortex can resolve gaps as small as 3 ms. While the differences in results were most likely due to different recording techniques, it is evident that the primary auditory cortex plays a central role in auditory temporal processing.
Related Knowledge Centers
- Auditory System
- Cochlear Nucleus
- Cortical Deafness
- Hearing
- Lateral Sulcus
- Planum Temporale
- Superior Temporal Gyrus
- Transverse Temporal Gyrus
- Temporal Lobe
- Brodmann Areas 41 & 42