A cortical implant is a subset of neuroprosthetics that is in direct connection with the cerebral cortex of the brain. By directly interfacing with different regions of the cortex, the cortical implant can provide stimulation to an immediate area and provide different benefits, depending on its design and placement. A typical cortical implant is an implantable microelectrode array, which is a small device through which a neural signal can be received or transmitted.

The goal of a cortical implant and neuroprosthetic in general is "to replace neural circuitry in the brain that no longer functions appropriately."

Cortical implants have a wide variety of potential uses, ranging from restoring vision to blind patients or helping patients with dementia. With the complexity of the brain, the possibilities for these brain implants to expand their usefulness are nearly endless. Some early work in cortical implants involved stimulation of the visual cortex, using implants made from silicone rubber. Since then, implants have developed into more complex devices using new polymers, such as polyimide. There are two ways that cortical implants can interface with the brain, either intracortically (direct) or epicortically (indirect). Intracortical implants have electrodes that penetrate into the brain, while epicortical implants have electrodes that stimulate along the surface. Epicortical implants mainly record field potentials around them and are generally more flexible compared to their intracortical counterparts. Since the intracortical implants go deeper into the brain, they require a stiffer electrode. However, due to micromotion in the brain, some flexibility is necessary in order to prevent injury to the brain tissue.

Certain types of cortical implants can partially restore vision by directly stimulating the visual cortex. Early work to restore vision through cortical stimulation began in 1970 with the work of Brindley and Dobelle. With their initial experimentation, some patients were able to recognize small images at fairly close distances. Their initial implant was based on the surface of the visual cortex and it did not provide as clear of images that it could, with an added downside of damage to surrounding tissues. More recent models, such as the "Utah" Electrode Array use deeper cortical stimulation that would hypothetically provide higher resolution images with less power needed, thus causing less damage. One of the major benefits to this method of artificial vision over any other visual prosthetic is that it bypasses many neurons of the visual pathway that could be damaged, potentially restoring vision to a greater number of blind patients.

However, there are some issues that come with direct stimulation of the visual cortex. As with all implants, the impact of their presence over extended periods of time must be monitored. If an implant needs to be removed or re-positioned after a few years, complications can occur. The visual cortex is much more complex and difficult to deal with than the other areas where artificial vision are possible, such as the retina or optic nerve. The visual field is much easier to process in different locations other than the visual cortex. In addition, each areas of the cortex is specialized to deal with different aspects of vision, so simple direct stimulation will not provide complete images to patients. Lastly, surgical operations dealing with brain implants are extremely high-risk for patients, so the research needs to be further improved. However, cortical visual prostheses are important to people who have a completely damaged retina, optic nerve or lateral geniculate body, as they are one of the only ways they would be able to have their vision restored, so further developments will need to be sought out.

Advancements in visual implants focus on stimulating specific areas of the visual cortex. The middle temporal (MT) region, crucial for perceiving motion, is a key target for electrical stimulation to create smooth motion artificially. Precise electrode implantation in MT poses a challenge due to its location, which is surrounded by sulci. Ongoing research explores multi-area stimulation between MT and primary visual cortex (V1), aiming to understand its impact on generating phosphenes (visual illusion) and motion perception. This multi-area approach, targeting different regions in the visual system, holds promise for improving the clarity and performance of visual implants, offering a potential avenue for more effective vision restoration.

While there has been little development in developing an effective auditory prosthesis that directly interfaces with the auditory cortex, there are some devices, such as a cochlear implant, and an auditory brainstem implant, introduced by Dr. William House and his team, that have been successful in restoring hearing to deaf patients. The cochlear implant targets the cochlear or auditory nerve, and individuals who have issues with this nerve can never benefit from it. As an alternative, the auditory brainstem prosthesis can be used.

There have also been some studies that have used microelectrode arrays to take readings from the auditory cortex of animals. One study has been performed on rats to develop an implant that enabled simultaneous readings from both the auditory cortex and the thalamus. The readings from this new microelectrode array were similar in clarity to other readily available devices that did not provide the same simultaneous readings. With studies like this, advancements can be made that could lead to new auditory prostheses.