Havana (CNN) A Cuban government investigator looking into reports of mysterious acoustic attacks on US and Canadian diplomats on the communist-run island on Monday dismissed a US government theory that microwave weapons emitting concentrated beams of radiation may have been used in the incidents. 
 
 "If you look at the alleged events, there have been reports that there are several people in a room with thick walls and thick windows and only one person was targeted. This is a kind of weapon that doesn't exist," said Dr. Mitchell Valdes-Sosa, a well-known neurologist who is part of the Cuban special task force investigating the alleged attacks. "It's science fiction, not science," he said. 
 
 "First, it was sonic weapons, now microwave. What's next, kryptonite?" the investigator said in an interview with CNN at his research center in Havana, referring to an earlier theory that sonic weapons emitting high-powered ultrasound waves could have caused the injuries. 
 
 Valdes-Sosa said researchers and investigators are working on a paper to rebut the microwave weapons theory. 
 
 Previously, the government not only denied involvement in the attacks but cast doubt on whether they actually occurred. In June, Cuba's Foreign Ministry said "political motivations" drove the United States to withdraw its embassy personnel. 
 
 Though a March report based on the examinations of 21 diplomats who served in Cuba didn't link the attacks to microwaves, the study's lead author, Douglas Smith, director of the University of Pennsylvania's Center for Brain Injury and Repair, told The New York Times that US diplomats in Cuba and China likely suffered brain injuries and that microwaves are considered the culprit. 
 
 Valdes-Sosa said for a microwave weapon to work it would have to been used at a close distance, and none of the diplomats reported seeing the alleged perpetrators. He said that Cuban authorities had investigated the report that one diplomat who suffered an apparent attack had seen a van speed off and that the vehicle belonged to a church. 
 
 While the US has not directly blamed the Cuban government for carrying out the attacks, US officials said Cuba is responsible for safeguarding the diplomats well-being and that Cuban officials would likely know if a third government were responsible. 
 
 But Valdes-Sosa said after more than a year of US, Canadian and Cuban investigations there was still no hard proof that any attacks actually took place. 
 
 "For an attack to have occurred you have to have a real victim. First the thing we are not sure is if all these people evacuated from Cuba are really ill or have suffered do something that happened to them," Valdes-Sosa said. "Second, you have to have a perpetrator. Who would be interested? You have to have the opportunity." 
 
 In a Sunday interview with CNN, Smith said microwaves are "a main suspect" in causing the diplomats' injuries, but ultrasound and infrasound were being studied as potential causes as well. 
 
 JUST WATCHED State Department pulls employees out of Cuba Replay More Videos ... MUST WATCH State Department pulls employees out of Cuba 02:34 
 
 "It's almost like a concussion, but without a concussion -- meaning that they look like individuals who have persistent concussion symptoms but have no history of head impact," Smith said, describing the injuries and explaining that learning the cause is vital to determining the best means of preventing it. 
 
 "Just like we have ways to prevent people from having a concussion, you could think of maybe protecting your brain from these energy sources," he said. 
 
 Most of the attacks came in 2016 and 2017, though there have been a handful of reported incidents this year as well. 
 
 A senior administration official told CNN that investigators have torn apart buildings where diplomatic employees encountered the sounds but found no acoustic devices, leading law enforcement to believe that the injuries were the result of microwaves beamed from a nearby location and that the "sounds" were merely a means of masking the microwave attacks. 
 
 This is only a theory, the official said, and there is no concrete evidence to back it. However, brain scans on the injured personnel showed changes that indicate damage, the official said. 
 
 JUST WATCHED Trump: Cuba 'responsible' for diplomat attacks Replay More Videos ... MUST WATCH Trump: Cuba 'responsible' for diplomat attacks 00:18 
 
 In a statement, the US State Department on Sunday neither confirmed nor denied the possibility that microwaves were behind the diplomatic injuries. 
 
 "The health and well-being of our personnel remains our top priority," the statement said. "The investigation into the origin of these symptoms continues. The inter-agency community is working diligently to determine the cause of the symptoms, as well as to develop mitigation strategies." 
 
 Secretary of State Mike Pompeo said earlier this year he was establishing a Health Incidents Response Task Force , led by Deputy Secretary of State John Sullivan and including representatives from the departments of Justice as well as Health and Human Services. 
 
 The task force will serve as the "coordinating body for department and interagency activities, including identification and treatment of affected personnel and family members, investigation and risk mitigation, messaging, and diplomatic outreach," Pompeo said in a statement. 
 
 The sophistication of the attack has led US officials to suspect a third country is involved, perhaps as retribution against the United States or Canada -- whose diplomats have also been targeted -- or to drive a wedge between those countries and Cuba. 
 
 In August 2017, officials included Russia among a list of countries that have an adversarial relationship with the United States and that American investigators suspected might be involved. ||||| It reads like a bad spy thriller. Between November 2016 and October 2017, a strange illness afflicted 24 diplomatic staff members working at the U.S. embassy in Havana, Cuba. Employees reported symptoms such as headaches, confusion, hearing loss. They talked about hearing strange sounds, triggering speculation the Cubans were employing a new acoustic weapon to harass embassy employees. Other scientists dismissed the idea of a sonic weapon as impractical. 
 
 On September 1 science reporter William Broad jumped into this morass with a long article in The New York Times. His theory: the Cubans were employing a microwave weapon against U.S. embassy employees, causing sonic delusions and “very real brain damage”. He based his theory on the microwave auditory effect, in which pulses of microwave energy of the sort emitted by radar elicits auditory sensations in exposed individuals. 
 
 As the scientist who first proposed the now-accepted explanation of the effect in my 1974 Science article, I find the theory wildly implausible. To elicit auditory sensations, individuals must be exposed to intense but brief (microsecond) pulses of microwave energy. The pulses are sufficient to heat brain tissue by a few microdegrees in a few microseconds, and the resulting thermal expansion launches an acoustic wave in the brain that the subject perceives as sound. The acoustic pressures are many orders of magnitude too weak to cause tissue damage. They elicit audible sensations only because of the exquisite sensitivity of the human auditory system, and represent a near-threshold hearing phenomenon. To actually damage the brain, the microwaves would have to be so intense they would actually burn the subject, which has never happened in any of these incidents. 
 
 To induce such an effect, one could cobble together a device from a military radar set or a commercial microwave generator, such as the one I used in my original experiments, and then direct a beam at a distant target. But the difficulty of aiming the beam at a person’s head some distance away would be daunting. You would have to know exactly where the victim’s head is located. You could use a much higher power radar such as that used for airport traffic control and spray the beam over a wide area, but the equipment then would be very large and cumbersome. Microwave antennas could also be embedded within the embassy walls, along with some kind of aiming device, but they would be easy to detect. 
 
 But why bother with a device that produces near-threshold hearing sensations? There are simpler ways to harass people if that is the goal. Even now, a year after the incidents were reported, the facts of the matter remain unclear. A follow-up medical examination of 21 of the affected individuals by a neuroscience group led by Doug Smith at the University of Pennsylvania (my colleagues, in fact) found equivocal evidence the individuals had sustained “injury to widespread brain networks”. Neuroskeptic, a neuroscientist who blogs anonymously in Discover magazine, brutally reviewed the Penn study. The blogger and other critical scientists suggested the findings were statistical artifacts due to the many tests the Penn group employed on the subjects. Other scientists have argued psychological factors were involved instead. Taken together, the results seem too scattered to allow firm conclusions to be drawn. 
 
 In October 2017 Josh Lederman and Michael Weissenstein from the Associated Press made recordings available of the sounds that the employees reported hearing. If those indeed were the sounds, that would rule out the microwave auditory effect where the microwave-induced vibrations exist only within the head. Chen Yan, Kevin Fu and Wenyuan Xu (of Zhejiang University and the University of Michigan) showed the sounds in the AP recordings are characteristic of those produced by the interaction of two inaudible ultrasound beams via an effect known as intermodulation distortion. Ultrasound is widely used in burglar detectors, room occupancy sensors and other increasingly common appliances, and some individuals report unpleasant audible sensations from such devices. Intermodulation distortion is increasingly being employed to jam microphones used to record concert music illegally or for eavesdropping. Yan and colleagues report ultrasound can be used for eavesdropping purposes as well, by picking up vibrations in objects produced by human speech. 
 
 In short, it is reasonable to guess the sounds were inadvertently produced by ultrasound devices, possibly even spy tech, but without malicious intent against the embassy personnel. The incidents occurred about the time of the 2016 U.S. election, and the Cubans undoubtedly were desperate for intelligence about U.S. intentions. 
 
 There is even a historical parallel to the recent incidents: In 1972 it became publicly known the Soviets had been irradiating the U.S. embassy in Moscow with low-level microwave energy from the 1950s through the 1970s. Neither side disclosed the reason for this. (A reasonable guess is the Russians were trying to disrupt U.S. listening equipment or to collect data from their own bugs in the building.) The media published hyperbolic stories about supposed attempts to harm the embassy staff, fueling a generation of speculation about microwave “neurowarfare.” 
 
 We don’t know all the facts about the earlier incidents or the current ones, and no government is likely to provide them. Much of the information available is distinctly anecdotal. The Times story is not “fake news” but the real facts of the matter may be quite different from those presented by its distinguished journalist. ||||| Ten scientists have published letters in the Journal of the American Medical Association criticizing the first medical review of the US diplomats in Cuba who were reportedly targets of a “sonic attack.” 
 
 In letters published by JAMA on Tuesday, the scientists complained that the authors of a February study in the journal failed to include “mass hysteria” as one of the possible causes of the symptoms that the diplomats reported. Such “mass psychological outbreaks” usually take place in high-stress environments, and all involved begin exhibiting the similar, real physical symptoms. 
 
 The critics also said the study’s authors did not include information on whether the diplomats had known one another, and included no testing on hearing and balance — even though “a presumed sonic weapon attack would affect the inner ear more preferentially than any other part of the body, including the brain.” The inner ear is critical to balance. 
 
 The letters are the latest broadside in what has become a contentious scientific battle that has raged since the Trump administration first used the reports of “sonic attacks” on diplomats in Cuba to justify withdrawing diplomats from the island, expelling Cuban diplomats from Washington, cutting back on contacts between the United States and Cuba, and advising US citizens not to travel to the island. 
 
 Some scientists challenged the State Department’s assertions that some sort of sonic attack was responsible for the vague symptoms diplomats complained of, including hearing loss and cloudy thinking, and the US government eventually stopped using the word “attack” to describe what took place. But the US also declared that Havana was too dangerous to allow diplomats’ families to live there. 
 
 The February JAMA article was touted as the first scientific assessment of the evidence. In it, University of Pennsylvania researchers ruled out a sonic attack, neurological illness from a tropical virus, or poisoning as possible explanations. Rather, the 21 individuals they examined showed a “constellation” of symptoms that suggested concussions, without the head trauma. “If you didn’t know their history, they would look to you like other concussion patients,” the study’s lead author, Randel Swanson, told BuzzFeed News at the time. 
 
 The study also said they displayed cognitive dysfunction and abnormalities. 
 
 The letters published Tuesday were all critical of the authors’ conclusions. Written by physicians and researchers from a variety of states and nations, the letters questioned the assessment, saying the authors had not done critical tests and had improperly interpreted the results of cognitive tests. Crucially, according to one expert, the Penn team had failed to consider evidence that the illness could be a form of a mass psychological outbreak — for which there is no immediate external cause. 
 
 Robert Bartholomew, an American-born medical sociologist at Botany Downs Secondary College in New Zealand, and a main proponent of the idea that diplomats were or are suffering a psychological outbreak, argued that the authors of the study were unduly dismissive of “mass psychogenic illness,” also known as “mass hysteria,” because there was no rapid onset and recovery. “However,” Bartholomew wrote, “the second most common type of mass psychogenic illness begins slowly and persists for months or years and often features neurological symptoms.” 
 
 Bartholomew also criticized the study’s lack of “social network analysis” — determining whether patients actually knew one another. For a mass psychological outbreak to occur, the individuals involved would have needed to know one another; the study notes that some of the individuals involved did not know one another. 
 
 But Bartholomew said relying on the patients for that information was inadequate since the study took place 203 days after the first victims reported their symptoms. They may have misremembered contacts, or, he argues, the patients didn’t actually need to know one another personally. They only needed to know others were ill. 
 
 Earlier this year, a US government employee in China reported similar symptoms, and US Secretary of State Mike Pompeo said the two cases were “very similar and entirely consistent.” 
 
 Other scientists and doctors — from Edinburgh, UK; Bochum, Germany; Salisbury, North Carolina; Denver, Colorado; Covington, Louisiana; and New Brunswick, New Jersey — wrote in too. 
 
 Gerard Gianoli and James Soileau of the Ear and Balance Institute in Covington, joined by P. Ashley Wackym of Rutgers University's Robert Wood Johnson Medical School, noted that the study didn’t include testing on hearing and balance, even though “a presumed sonic weapon attack would affect the inner ear more preferentially than any other part of the body, including the brain.” 
 
 Robert Shura and Holly Miska of the Salisbury Veterans Affairs Medical Center and Jason Kacmarski of the Veterans Affairs Eastern Colorado Health Care System criticized the study for what they said was its “improper interpretation of objective cognitive test results.” They write that the University of Pennsylvania researchers chose a more “liberal cutoff” to define impairment than would normally be used in research settings. Their conclusion that the patients “had significant areas of cognitive weakness and/or impairment,” they write, is based on a “misapplication of common interpretive classification systems.” 
 
 The letters also challenged the idea that a disorder or mass psychogenic illness is somehow less real or more the fault of the individuals involved than, say, a concussion. “Although diagnostic caution is warranted, functional neurological disorders are common genuine disorders that can affect anyone,” wrote Jon Stone and Alan Carson of Edinburgh and Stoyan Popkirov of Bochum, adding, “including hardworking diplomatic staff.” 
 
 In a response published in JAMA immediately below the letters, the University of Pennsylvania team defended its work, writing that the chronic symptoms they found “are entirely different” from those seen in mass psychogenic disorders. They also said they “must continue to withhold certain sensitive information,” although they do not say why and do admit the US State Department cleared the study as a public health matter. 
 
 The US government has sent FBI agents to Cuba to study the illness, but has yet to reach a conclusion on its cause. In July, the Centers for Disease Control and Prevention joined the investigation into what injured the diplomats. 
 
 The Cuban Embassy in Washington did not immediately reply to request for comment. The American Foreign Service Association, which represents US diplomats, would not comment prior to publication of the letters, which they had not seen. JAMA declined to comment on why the criticism was published six months after the study, or whether the US government pressured it into publishing the study in the first place.
– Microwave weapons? That's the latest theory being floated to explain the mysterious ailments suffered by staffers at the American embassy in Cuba. But now a pioneering scientist in that field thinks the idea—based on a principle called the microwave auditory effect—is bogus. Kenneth Foster is a professor of bioengineering at Penn who explained the auditory effect in a 1974 study. At Scientific American, he assesses what's known about the Cuban ailments and lays out why it's "wildly implausible" that microwaves are to blame. For one thing, any such weapon powerful enough to cause brain damage would almost certainly burn the victims, too, and that didn't happen. Instead, Foster suggests that a much simpler explanation is likely. "It is reasonable to guess the sounds were inadvertently produced by ultrasound devices, possibly even spytech, but without malicious intent against the embassy personnel," he writes. Foster cites this earlier investigation from the AP revealing the sounds that the victims are believed to have heard, and he says the sounds are consistent with ultrasound devices interacting with each other. It makes sense to him that the Cubans might have been trying to listen in on Americans with these relatively common gizmos. "The incidents occurred about the time of the 2016 US election, and the Cubans undoubtedly were desperate for intelligence about US intentions." A Cuban scientist, meanwhile, agrees that the microwave theory is far-fetched. "First, it was sonic weapons, now microwave," he told CNN. "What's next, kryptonite?"