That is like being struck by 20 lightning bolts
50Tbps of data would require 400 trillion electrical impulses a second. Keep in mind that the brain works at MUCH higher voltages and lower frequencies than a microprocessor; so, at 70 milivolts per impulse, you'd need to input about 6 billion volts of electricity to do this. That is 20 times the voltage of an average lightning bolt directed straight into a person's head. Not only would this much electricity cause the person's brain to explode, but probably the whole room he was standing in along with him.
That said, there is no reason any sane person would install electrodes in their brain that are capable of inputting this much data. In all likelihood, the manufacturer of the electrodes would not make it possible for the electrodes to transmit at more than 70 milivolts meaning that you could not make an impulse strong enough to overcome a neuron's minimum sensitivity threshold to constitute any change in the brain state AND fast enough to transmit data faster than the neurons can handle, in this case what you are suggesting is impossible. The input device would cap out at what the brain can handle, and there is nothing hazardous to worry about as the recipient. At most, a low frequency random noise generator could cause some weird hallucinations and memory interference, and make it really hard to focus on anything happening outside of your mind... but once the attack is over, your brain would resume normal function just like an IRL DDoS attack.
Now, a non-random attack could perhaps shut down control over the parts of your brain that regulate vital organs... but again, what kind of manufacturer would create electrodes that could interfere with vital brain functions. Any half thought out brain implant will only give the interface access to parts of the brain that can't kill you.
Original Answer Below invalidated by Changes to the question
They are doable, and quite common
First, lets clarify that a DoS (Denial of Service) attack is specifically an attack that sends fake or pointless requests to a system such that you use up its ability to process them all so that you prevent the system from processing important jobs. An effective DoS attack balances requiring a lot of time and resources of the target, and minimal time and resources of the attacker allowing a bad actor to invest little resources to cause a lot of wasted resources of the victim. A DDoS (Distributed Denial of Service) attack is a specific kind of DoS attack where you use a group of attackers instead of one. This does 2 things: (1) it can make it harder to filter out spam requests from legitimate requests and (2) it opens up more avenues of attack by taking less work on the primary attackers part if he's offloading most of the spam work itself onto other systems. DDoS attacks are often not done by a group of bad actors, but a single bad actor who's tricked innocent actors into performing requests on their behalf.
Social DDoS Attacks
To picture how this can work against humans on a social level, imagine there is a restaurant that has a policy that lets you order a meal, and then pay for it when you pick it up. Now imagine you want to deprive the real customers of service for some reason. You could call in an order of 200 hamburgers forcing the kitchen to stop processing real orders to fill your 200 hamburger order... then you just never show up to pay. This is a denial of service attack performed against the human brain because the human brain requires a lot of processing to respond to this simple request. But... humans can easily tell that a 200 burger order is sketchy and filter it out of normal orders by deprioritizing it... just like computer DoS attacks are pretty easy to recognize and control through good load balancing.
This is where the "Distributed" part of a DDoS attack comes in. Instead of calling in 1 order for 200 burgers, you could call in 100 orders for 1-3 burgers each. Because these orders are all normal orders in appearance, the restaurant's cook does not know how to filter or prioritize the fake orders; so, they have to make all the orders with the same priority causing a less controllable denial of service to real customers.
But, just like good software design can minimize but not eliminate the impact of a DDoS attack, good thinking can minimize a DDoS against a human system as well. You do this by minimizing how much a malicious actor can ask of you before they prove they are not a malicious actor. For example, your restaurant can start asking to validate the credit card before they take the order so they can't waist your time and kitchen materials on a fake order... granted, you can still DDoS a restaurant by keeping their receptionist busy with fake, short phone calls, but this takes a lot more effort of the attacker to actually overwhelm the human system.
This is of course just one example, but any time you maliciously ask a lot of things of someone just to keep them too busy to do what they want/need to do, it is some kind of DoS attack. If you have kids, you probably handle several social DDoS attacks a day.
Neurological DDoS attacks
The human neurological system can also be directly DoSed. Every time someone falls victim to any kind of slight of hand or misdirection, they have been DoSed. Most human senses are processed by the thalamus before making its way to the prefrontal cortex for selective processing. The human mind is constantly flooded with about 10x more input than we can consciously process, and our thalamus/PFC makes sure that only as much input makes it through for processing as we can handle. If your mind is busy working on solving (or ignoring) a problem, you will consciously see/hear/feel less to make sure you don't get overwhelmed. In layman's terms we call this "focus".
A guard will not notice a person slip by if they are distracted by a conversation. If you run into someone, all the simultaneous signals of being touched in a lot of places will make it so that you will not process the specific feeling of someone slipping their hand into your pocket to take your wallet. If a magician is breathing fire, you will not notice them swapping out the deck of cards on the table you are supposed to be keeping track of. All of these tricks rely on a form of DDoS attack to prevent the victim from processing something you don't want them to notice by filling their available processing power with distractions.
DOS, notDDOS. $\endgroup$